http://www.webmd.com/hw/health_guide_atoz/hw6580.asp A-Z Health Guide from WebMD: Medical Tests Urine Test Test OverviewA urine test measures several different components of urine, a waste product made by the kidneys. A routine urinescreening test may be done to help find the cause for many types of symptoms. The test can provide information aboutyour overall health and clues to many conditions.The kidneys remove waste material, minerals, fluids, and other substances from the blood for elimination in theurine. Therefore, urine can contain hundreds of different bodily waste products. Many factors, such as diet, fluid intake,exercise, and kidney function, affect what is in your urine.More than 100 different tests can be done on urine. A routine urinalysis usually includes the following tests. Color. Many factors affect urine color, including fluid balance, diet, medications, and disease. The intensity of the color generally indicates the concentration of the urine; pale or colorless urine indicates that it is dilute, and deep yellow urine indicates that it is concentrated. Vitamin B supplements can turn urine bright yellow. Reddish brown urine may be caused by certain medications; by blackberries, beets, or rhubarb in the diet; or by the presence of blood in the urine. Clarity. Urine is normally clear. This test determines the cloudiness of urine, also called opacity or turbidity. Bacteria, blood, sperm, crystals, or mucus can make urine appear cloudy. Odor. Urine usually does not smell very strong, but has a slightly "nutty" (aromatic) odor. Some diseases can cause a change in the normal odor of urine. For example, an infection with E. coli bacteria can cause a foul odor, while diabetes or starvation can cause a sweet, fruity odor. Specific gravity. This measures the amount of substances dissolved in the urine. It also indicates how well the kidneys are able to adjust the amount of water in urine. The higher the specific gravity, the more solid material is dissolved in the urine. When you drink a lot of liquid, your kidneys should produce greater- than-normal amounts of dilute urine (low specific gravity). When you drink very little liquid, your kidneys should make only small amounts of concentrated urine (high specific gravity). pH. The pH is a measure of how acidic or alkaline (basic) the urine is. A urine pH of 4 is strongly acidic, 7 is neutral (neither acidic nor alkaline), and 9 is strongly alkaline. Sometimes the pH of urine may be adjusted by certain types of treatment. For example, efforts may be made to keep urine either acidic or alkaline to prevent formation of certain types of kidney stones. Protein. Protein is normally not detected in the urine. Sometimes a small amount of protein is released into the urine when a person stands up (this condition is called postural proteinuria). Fever, strenuous exercise, normal pregnancy, and some diseases, especially kidney disease, may also cause protein in the urine. Glucose. Glucose is the type of sugar usually found in blood. Normally there is very little or no glucose in urine. However, when the blood sugar level is very high, as in uncontrolled diabetes, it spills over into the urine. Glucose can also be present in urine when the kidneys are damaged or diseased. Nitrites. Bacteria that cause a urinary tract infection (UTI) produce an enzyme that converts urinary nitrates to nitrites. The presence of nitrites in urine indicates a UTI. Leukocyte esterase (WBC esterase). Leukocyte esterase detects leukocytes (white blood cells [WBCs]) in the urine. The presence of WBCs in the urine may indicate a urinary tract infection. Ketones. When fat is broken down for energy, the body produces by-products called ketones (or ketone bodies) and releases them into the urine. Large amounts of ketones in the urine may signal a dangerous condition known as diabetic ketoacidosis. A diet low in sugars and starches (carbohydrates), starvation, or prolonged vomiting may also cause ketones in the urine. Microscopic analysis. In this test, urine is spun in a centrifuge so the solid materials (sediment) settle out. The sediment is spread on a slide and examined under a microscope. Types of materials that may be found include: o Red or white blood cells. Normally blood cells are not found in urine. Inflammation, disease, or injury to the kidneys, ureters, bladder, or urethra can cause blood in urine. Strenuous exercise (such as running a marathon) can also cause blood in urine. White blood cells are often a sign of infection, cancer, or kidney disease. o Casts. Some types of kidney disease can cause plugs of material (called casts) to form in tiny tubes in the kidneys. The casts can then get flushed out into the urine. Casts can be made of different types of material, such as red or white blood cells, waxy or fatty substances, or protein. The type of cast can provide clues about the type of kidney disease that may be present.
o Crystals. Healthy people often have only a few crystals in their urine. However, a large number of crystals, or the presence of certain types of crystals, may indicate kidney stones or a problem with how the body is using food (metabolism). o Bacteria, yeast cells, or parasites. Normally there are no bacteria, yeast cells, or parasites in urine. Their presence can indicate an infection.Why It Is DoneA urine test may be done: To screen for a disease or infection of the urinary tract. Symptoms that may lead to a urine test include discolored or foul-smelling urine, pain during urination, difficulty urinating, flank pain, blood in the urine (hematuria), or fever. To monitor the treatment of certain conditions such as diabetes, kidney stones, a urinary tract infection (UTI), hypertension, or some types of kidney or liver disease. As part of a routine physical examination.How To PrepareDo not eat foods that can discolor the urine, including blackberries, beets, and rhubarb. Do not exercise strenuouslybefore a urine sample is taken.Tell your health professional if you are menstruating or within a few days of starting your menstrual period. Your healthprofessional may want to postpone the urine test, depending on the suspected problem.Because certain medications can discolor the urine, your health professional may instruct you to stop taking themedications prior to the test. Medications that can discolor the urine include vitamin B, phenazopyridine (Pyridium),rifampin, and phenytoin (Dilantin). Be sure to tell your health professional if you are taking diuretics, which may affectthe test results.Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will bedone, or what the results will indicate. To help you understand the importance of this test, fill out the medical testinformation form (What is a PDF document?).How It Is DoneA routine urine test can be done in your health professionals office, clinic, or lab. You may also be asked to collect aurine sample at home and bring it with you to the office or lab for testing.Clean-catch midstream urine collectionThis collection method prevents contamination of the sample. Wash your hands to make sure they are clean before collecting the urine. If the collection container has a lid, remove it carefully and set it down with the inner surface up. Avoid touching the inside of the container with your fingers. Clean the area around your genitals. o A man should retract the foreskin, if present, and clean the head of his penis thoroughly with medicated towelettes or swabs. o A woman should spread open the folds of skin around her vagina with one hand, then use her other hand to clean the area around her vagina and urethra thoroughly with medicated towelettes or swabs. She should wipe the area from front to back to avoid contaminating the urethra with bacteria from the anus. Begin urinating into the toilet or urinal. A woman should continue to hold apart the folds of skin around the vagina while she urinates. After the urine has flowed for several seconds, place the collection container into the stream and collect about 2 fl oz(59 mL) of this ―midstream‖ urine without interrupting the flow. Avoid touching the rim of the container to your genital area, and avoid getting toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample. Finish urinating into the toilet or urinal. Carefully replace the lid on the container and return it to the lab. If you are collecting the urine at home and cannot get it to the lab within an hour, refrigerate it.
Double-voided urine sample collectionThis collection method reflects the type of urine your body is producing right now. Empty your bladder by urinating into the toilet or urinal. Do not collect any of this urine. Drink a large glass of water and wait about 30 to 40 minutes. Follow the instructions above for collecting a clean-catch urine sample.The urine sample is then sent to a lab for analysis.How It FeelsCollecting a urine sample does not normally cause any discomfort.RisksThere are no risks associated with collecting a urine sample.ResultsA urine test measures several different components of urine, a waste product made by the kidneys. Normal results mayvary from lab to lab.Color Normal: Pale to dark yellow Abnormal: Many foods and medications can affect the color of the urine. Colorless urine may be caused by conditions such as long-term kidney disease or uncontrolled diabetes. Dark yellow urine can be caused by conditions such as dehydration. Reddish urine can be caused by blood in the urine.Clarity Normal: Clear Abnormal: Cloudy urine can be caused by pus (white blood cells), blood (red blood cells), sperm, bacteria, yeast, crystals, mucus, or a parasite infection (such as trichomoniasis).Odor Normal: Slightly "nutty" (aromatic) odor Abnormal: Some foods (such as asparagus), vitamins, and antibiotics (such as penicillin) can cause urine to develop an unusual odor. A sweet, fruity odor may be caused by uncontrolled diabetes. A urinary tract infection (UTI) can cause a foul odor. Urine that smells like maple syrup can indicate maple syrup urine disease, a condition caused by the bodys inability to break down certain amino acids.Specific Normal: 1.005–1.035gravity Abnormal: Abnormally high specific gravity indicates very concentrated urine, which may be caused by not drinking enough liquid, loss of too much liquid (excessive vomiting, sweating, or diarrhea), or substances (such as sugar or protein) in the urine. Abnormally low specific gravity indicates dilute urine, which may be caused by drinking excessive amounts of liquid, severe kidney disease, or the use of diuretics.pH Normal: 4.5–8.0 Abnormal: Some foods (such as citrus fruit and dairy products) and medications (such as antacids) can affect urine pH. A high (alkaline) pH can be caused by prolonged vomiting, a kidney disease, some urinary tract infections, and asthma. A low (acidic) pH may be a sign of severe lung disease (emphysema), uncontrolled diabetes, aspirin overdose, prolonged diarrhea, dehydration, starvation, drinking an excessive amount of alcohol, or drinking antifreeze (ethylene glycol).Protein Normal: None Abnormal: Protein in the urine usually indicates kidney damage or disease that can be caused by conditions such as an infection, cancer, high blood pressure, diabetes, systemic lupus erythematosus (SLE), or glomerulonephritis. Protein in the urine can also be caused by heart failure, leukemia, poison (lead or mercury
poisoning), or a condition during pregnancy that results in high blood pressure (preeclampsia).Glucose Normal: None Abnormal: Intravenous (IV) fluids can cause the presence of glucose in the urine. Excess glucose in the urine is often caused by uncontrolled diabetes. Other conditions that may cause glucose in urine include an adrenal gland problem, liver damage, brain injury, certain types of poisoning, and certain types of kidney diseases that decrease their ability to reabsorb glucose from the urine. Healthy pregnant women can have glucose in their urine which is normal during pregnancy.Ketones Normal: None Abnormal: Ketones in the urine can indicate poorly controlled diabetes, a very low-carbohydrate diet, starvation (including disorders that result in poor nutrition such as anorexia nervosa or bulimia), alcoholism, or poisoning from drinking rubbing alcohol (isopropanol). Ketones are often found in the urine when a person does not eat (fasts) for 18 hours or longer. This may occur when a person is sick and avoids food or vomits for an extended period of time. Low levels of ketones are sometimes found in the urine of a healthy pregnant woman.Microscopic Normal: Very few or no red or white blood cells or casts are seen. No bacteria, yeast cells, oranalysis parasites are present. A few crystals are usually normal. Abnormal: Red blood cells in the urine may be caused by kidney or bladder injury, kidney stones, a urinary tract infection (UTI), inflammation of the kidneys (glomerulonephritis), a kidney or bladder tumor, or systemic lupus erythematosus (SLE). White blood cells (pus) in the urine indicate a urinary tract infection, bladder tumor, inflammation of the kidneys, systemic lupus erythematosus (SLE), or inflammation under the foreskin of the penis or in the vagina. Depending on the type, casts can indicate inflammation or damage to the tiny tubes in the kidneys, poor blood supply to the kidneys, metal poisoning (such as lead or mercury), heart failure, or a bacterial infection. Excessive amounts of crystals, or the presence of certain types of crystals, can indicate kidney stones, damaged kidneys, or problems with metabolism. Some medications and certain types of urinary tract infections can also increase the number of crystals in urine. Bacteria in the urine indicate a urinary tract infection (UTI). Yeast cells or parasites (such as the parasite that causes trichomoniasis) can indicate an infection of the urinary tract.What Affects the TestFactors that can interfere with your test and the accuracy of the results include: Blood from a womans menstrual period. Medications, such as diuretics or high doses of vitamin C (ascorbic acid) taken with certain antibiotics (such as tetracycline). Some antibiotics, such as erythromycin and trimethoprim (Trimpex). Contrast material used in an X-ray test.What To Think About Some urine tests can be done using a home test kit. For more information, see the medical test Ketones or Home Test for Urinary Tract Infections. In some cases, the amount (volume) of urine produced in 24 hours may be measured. Most adults produce 1.3 qt(1.2 L) to 1.6 qt(1.5 L) of urine each day, with a normal range of about 1 qt(1 L) to 2 qt(2 L) per day. Children produce about 0.3 qt(0.3 L) to 1.6 qt(1.5 L) per day. Other substances that may be measured during a urine test include: o Bilirubin, a compound formed by the breakdown of red blood cells and normally eliminated from the body in stool. Bilirubin is not normally found in urine. If it is present, it usually means the liver is damaged or the flow of bile from the gallbladder is blocked. For more information, see the medical test Bilirubin. o Urobilinogen, a compound formed by the breakdown of bilirubin and eliminated from the body mostly in stool. Only small amounts of urobilinogen are normally found in urine. Urobilinogen in urine can be a sign of liver disease (cirrhosis, hepatitis) or blockage of the flow of bile from the liver or gallbladder.
o Bence Jones protein, an abnormal protein found in the urine of about 50% of people with a rare type of cancer called multiple myeloma. A urine test is usually done when multiple myeloma is suspected. The protein test done during a routine urine test does not usually detect Bence Jones protein. Collecting a urine sample from a small child or baby may be done by using a special plastic bag with tape around its opening. The bag is attached around the childs genitals until he or she urinates (usually within an hour). Then the bag is carefully removed. To collect a urine sample from a very sick baby, a health professional may insert a urinary catheter through the urethra or a needle through the babys abdomen directly into the bladder (suprapubic tap). To reduce the chance of contaminating the urine sample with bacteria (other than the bacteria causing the infection), a health professional may collect a urine sample by inserting a thin flexible tube (called a urinary catheter) through the urethra into the bladder. Catheterization is sometimes done to collect urine from a person in the hospital who is very ill or unable to provide a clean-catch sample (such as a child). This method reduces the risk that the sample will be contaminated, but it may occasionally cause a urinary tract infection (UTI). If an abnormal result is found during a urine test, additional tests may be done, such as a urine culture, X- ray of the kidneys (intravenous pyelography or IVP), or cystoscopy. For more information, see the medical tests Urine Culture, Intravenous Pyelogram (IVP), and Cystoscopy.CreditsAuthor Jan Nissl, RN, BSEditor Susan Van Houten, RN, BSN, MBAAssociate Editor Tracy LandauerPrimary Medical Reviewer Patrice Burgess, MD - Family MedicineSpecialist Medical Reviewer Philip Belitsky, MD, FRCSC - UrologyLast Updated December 7, 2004 UrinalysisUrinalysis begins with a macroscopic examination of the urine which describes the color and clarity ofthe urine. Many factors affect urine color including fluid balance, diet, medications and disease. Thefollowing table includes a list of the most common causes of abnormal urine coloration. Color Pathologic Causes Food & Drug Causes Cloudy Phosphorus, pyuria, chyluria, Diet high in purine-rich foods causing lipiduria, hyperoxaluria uricosuria Brown Bile pigments, myoglobin Fava beans, Levodopa, metronidazole (Flagyl), nitrofurantoin, anti-malarial drugs Brownish- Bile pigments, melanin, Cascara, levodopa, methyldopa, Senna Black methemoglobin Green or Pseudomonas UTI, biliverdin Amitriptyline, indigo, carmine, IV cimetidine Blue (Tagamet), IV promethazine (Phenergan), methylene blue, triamterene (Dyrenium) Orange Bile pigments Phenothiazines, phenazopyridine (Pyridium) Red Hematuria, hemoglobinuria, Beets, blackberries, rhubarb, Phenolphthalein, myoglobinuria, porphyria rifampin Yellow Concentrated urine Carrots, Cascara
Urine samples are initially screened with dipsticks. Performing microscopic analysis on only dipstickpositive urine samples is cost effective when the patient population being tested has a low incidence ofpotential disease. Numerous studies have determined that 6 to 20% of patients with urine sedimentabnormalities are missed by this testing strategy. However, most of the missed cases are clinicallyinsignificant and are often due to contaminating bacteria multiplying after urine collection. Urinedipsticks are plastic strips with attached reagent pads for pH, protein, glucose, ketone, bilirubin,urobilinogen, blood, nitrite, and leukocyte esterase. The principle and performance of each dipstick testis summarized below.pHThe test is based on a double indicator method (methyl red and bromthymol blue) that covers the entirerange of urine pH. Colors range from orange through yellow and green to blue. pH should be measuredin fresh urine and read quickly.The pH of urine is an indication of the kidneys ability to maintain a normal plasma pH. Metabolismproduces acids that are excreted by the lungs and kidneys. The average adult urine pH varies between 5and 8. A diet high in protein produces a more acid urine, while a vegetarian diet often produces a pHgreater than 6. Heavy bacterial growth may cause an alkaline shift in urine pH by converting urea toammonia. Pigmented urine can interfere with pH readings.Bacterial contaminants, blood in the urine and contamination by genital secretions can alter urine pH.ProteinThe protein test is based on a change in color of a pH indicator (e.g. tetrabromophenol blue) in thepresence of varying concentrations of protein when the pH is held constant. The reagent pad containsthe indicator and a buffer that holds the pH of the pad at approximately 3. Yellow indicates undetectableprotein. The color of positive reactions ranges from yellow-green to green to green-blue. The accuracy ofthis test depends on having urine that is slightly acidic. Dipsticks can detect protein concentrations aslow as 5 to 30 mg/dL. Urine protein concentrations are reported as 30, 100, 300, or 2000 mg/dL.This test is optimized to detect albumin and is less sensitive in detecting globulins. Dipsticks do notdetect beta-2- microglobulin or immunoglobulin light chains. Standard urine dipsticks are much lesssensitive at detecting urine albumin than other assays. Dipsticks do not detect microalbuminuria. Sensitivity Method Typical Detection Limit(mg/dL) (Relative to Urine Dipstick) Dipstick Protein 18 1 Spectrophotometric Urine Protein 6 3X more sensitive Immunoassay for Urine Albumin 0.3 60X more sensitiveDipstick testing is useful only when urinary protein exceeds 300 to 500 mg/day or albumin exceeds 10to 20 mg/day.The major cause of a false positive urine protein is a highly alkaline sample. False positive reactions canalso be caused by contamination with quaternary ammonium compounds (zepharin, chlorhexidine) usedto clean the skin for a clean catch urine. Excessive contact with urine may wash out the bufferingsystem and lead to a false positive result. Confirmatory tests only need to be performed on those urinesamples with positive protein and a pH of 7.5 or greater.Proteinuria can have many causes. Postural proteinuria occurs in 3 to 5% of healthy adults and ischaracterized by the presence of protein in the urine during the day but not the night. Strenuousexercise, fever, and exposure to extreme heat or cold, pregnancy, eclampsia, shock, and CHF causefunctional proteinuria. Hematologic malignancies, such as multiple myeloma, may produce excessimmunoglobulin that is excreted in the urine. Renal diseases are a common source of proteinuria.Approximately 25% of urine specimens containing bacteria will have a positive protein reaction as theonly positive dipstick reaction. The esterase reagent is sensitive to 15 leukocytes per hpf, but the protein
reagent is sensitive to 6 leukocytes per hpf.GlucoseThe dipstick test is based on a double enzyme method employing glucose oxidase and peroxidase. Colorchange ranges from green to brown. Small amounts of glucose (< 15 mg/dL) are normally excreted bythe kidney, which is below the 75 mg/dL lower limit of detection of dipsticks, Glucose oxidase is specificfor glucose and does not react with lactose, galactose, fructose, or reducing metabolites of drugs.Glucose is reported as 100, 250, 500, 1000, or >1000 mg/dL.Urine specific gravity and temperature may affect test reactivity. High urine specific gravity can reducecolor development. Urine should be at room temperature before the test is performed to obtain optimumsensitivity. False positive reactions rarely occur, but may be produced by strong oxidizing cleaningagents. Beta lactam antibiotics such as the penicillins, cephalosporins, carbapenems, and monobactamscan cause false positive reactions. Massive amounts of ascorbic acid (vitamin C), salicylates or levodopacan decrease the sensitivity of the test.Negative urine samples from pediatric patients under the age of one should be confirmed with a copperreduction method, such as Clinitest, to detect galactose or lactose. Confirmation only needs to beperformed once on a patient.Glucosuria usually occurs when the blood glucose level exceeds 180 mg/dL. Glucosuria most commonlyoccurs in patients with diabetes, infections, myocardial infarction, liver disease, and obesity. Thiazides,corticosteroids, and birth control pills may precipitate glucosuria.KetonesDipsticks use the nitroprusside reaction to test for acetoacetic acid. They are less sensitive to acetoneand do not detect beta-hyroxybutyrate. The typical diabetic patient with ketoacidosis usually excretes78% beta-hyroxybutyrate, 20% acetoacetate, and 2% acetone. The reaction of acetoacetic acid withnitroprusside results in the development of color ranging from buff pink to shades of purple. Colorreactions are categorized as trace, small, moderate and large that correspond to ketone concentrationsof 5, 15, 40 to 80 and 80 to 160 mg/dL of urine, respectively. Dipsticks reliably detect ketoneconcentrations of 40 mg/dL or more, so moderate and large readings do not need to be confirmed. Traceand small readings should be confirmed by using Acetest. The detection level for Acetest tablets is 20mg/dL. The presence of ketonuria does not signal the need to do further microscopic evaluation.Normally, urine contains < 2 mg/dL of acetoacetic acid, which is not detectable. A healthy individualmay have detectable ketones if he/she has been fasting, strenuously exercising, or is pregnant. Ketonesare also detected in children consuming high fat diets. Ketonuria is commonly seen in hospitalizedpatients due to fasting. Ketones are clinically significant only in the presence of urine glucose. Drugswith free sulfhydryl groups such as penicillamine, N-acetylcysteine, BAL and ACE inhibitors (captopriland enalapril) cause false positive reactions.Ketones are volatile and evaporate from the specimen with time. False negative results can occur withold urine samples. The reagent pads are extremely sensitive to moisture and may become non-reactiveafter exposure to humid room air for a few hours.BloodThe dipstick test for blood is based on the peroxidase-like activity of hemoglobin. Red cells are lysed oncontact with the strip, allowing free hemoglobin to catalyze the liberation of oxygen from organicperoxide. Tetramethylbenzidine is oxidized, producing a color change from orange to green-blue. Ifintact red cells do not lyse, they may produce speckles on the pad. The sensitivity of dipsticks forhemoglobin is 0.015 to 0.062 mg/dL. This concentration corresponds to 5 to 21 RBCs/uL or 1 to 4RBCs/hpf of concentrated urine sediment.The reference range for RBCs in normal urine is 0-3 RBC/hpf in males and 0-12 RBCs/hpf in femaleswhen concentrated urine sediment is examined. This range corresponds to a concentration of 3 to 20RBCs/uL of urine. Dipstick sensitivity extends into the reference range. Therefore, trace to 1+ readingmay be obtained on urine from as many as 3% of healthy individuals.In healthy individuals, fewer than 1000 red cells are excreted in the urine per minute. When 3000 to4000 red cells are excreted per minute, 2 to 3 red cells will be seen per high power field, indicatingmicroscopic hematuria. Gross hematuria occurs when more than 1 million red cells are excreted perminute. Hematuria can be due to lesions within the GU tract involving the kidneys, ureters, bladder,prostate, or urethra. The most common disorders include cancer, kidney stones, renal disease, urinarytract infection, and benign prostatic hyperplasia. Transient hematuria can result from menstruation, viral
illnesses, strenuous exercise, and mild trauma. Anticoagulant therapy and chemotherapy may also causehematuria. No etiology can be determined in approximately 45% of cases of microscopic hematuria.A positive dipstick test for blood does not tell whether the reaction is due to red cells, red cell casts,hemoglobin casts, or myoglobin. Many conditions can lead to discrepant dipstick and microscopicfindings. Any situation that causes red cell hemolysis will give a positive dipstick and negativemicroscopic result. Urine should be tested shortly after collection because red cell lysis may occur as thesample ages, if the pH is alkaline, or if the specific gravity is 1.010 or less. Bacterially contaminatedurine specimens may contain sufficient peroxidase activity to produce a false positive reaction. Falsepositive reactions can also be caused by vegetable peroxidase. False Positive Dipstick False Negative Dipstick Myoglobin Dipsticks exposed to air Oxidizing agents - bleach, detergent, iodine RBCs settle out & urine not mixed Bacterial peroxidase Ascorbic acid (high concentration) Vegetable peroxidase Formaldelhyde (preservative tablets) Betadine High specific gravity Very high protein Urine pH <5.1 High nitrite from UTI Captopril (Capoten)BilirubinThe bilirubin dipstick test detects conjugated bilirubin and has a sensitivity of 0.5 to 1.0 mg/dL. This testis based on the binding of conjugated bilirubin to diazotized salts fixed in the test pad in a strong acidicenvironment to produce a colored compound that is various shades of tan or magenta. Positive dipsticktests are confirmed with the Ictotest. Normal adult urine contains about 0.02 mg/dL of bilirubin, which isnot detectable by even the most sensitive methods. Confirmation of positive dipstick bilirubin results ismost valuable when the urine specimen is pale yellow.Ictotest is a tablet test that uses a similar chemical reaction but a different test environment. Urine isplaced on an absorbent test mat that captures substances within the urine. The reagent tablet is thenplaced on top of the absorbed urine and water is added to the tablet. The water dissolves the soliddiazonium salt and acid in the tablet so that they run onto the mat. The reaction of conjugated bilirubinwith the diazonium salt in the acid environment results in the formation of a blue ring around thedissolving tablet. The sensitvity of the tablet test is 0.05 to 0.1 mg/dL, which is about 10 times moresensitive than the dipstick test. The tablet test is also more specific than the dipstick test for bilirubinand its primary use is the detection of false positive dipstick reactions. Since the urine is placed on themat first in the tablet test, abnormal pigments due to medications or blood metabolites can be detectedbefore the chemical reaction ensues. Other interfering substances are washed through the mat and donot come into contact with the diazonium salt. Also, because the reaction product is blue rather than tanor magenta, fewer interpretation problems are encountered. Examples of medications that produce falsepositive dipstick and negative Ictotest results include rifampin, phenazopyridium (Pyridium), andnonsteroidal antiinflammatory agents (etodolac, mefenamic acid and flufenamic acid).Bilirubin and urobilinogen tests are valuable in detecting hemolysis, hepatic dysfunction, and biliaryobstruction. The results of these two tests should be interpreted together. Bilirubin is unstable andrapidly decomposes during exposure to light. False negative reactions are common if urine is not testedshortly after collection. Chlorpromazine (Thorazine) and selenium can produce false negative results.UrobilinogenMost dipsticks use para-dimethylaminobenzaldehyde in a strongly acid medium to test for urobilinogen.A positive reaction produces a pink-red color. Urobilinogen is normally present in urine at concentrationsup to 1.0 mg/dL. A result of 2.0 mg/dL represents the transition from normal to abnormal. False positive
results can be caused by medications such as para-aminosalicylic acid, antipyrine, chlorpromazine,phenazopyridine, phenothiazine, sulfadiazine, and sulfonamide. High nitrite concentrations can causefalse negative reactions. Pigmented urine can interfere with detection of urobilinogen.Conjugated bilirubin is normally excreted into the bowel where bacteria metabolize it to urobilinogen.Urobilinogen is partially reabsorbed from the gut and excreted in the urine. A positive test indicatesincreased bilirubin delivery to the gut. Hepatitis produces positive urine bilirubin and urobilinogen. Biliarytract obstruction results in positive urine bilirubin but negative urobilinogen. Hemolytic anemia causesnegative urine bilirubin and positive urobilinogen. Disease Urobilinogen Bilirubin Healthy Normal Negative Icteric liver disease Increased Positive Biliary obstruction Absent Positive Hemolytic anemia Increased NegativeLeukocyte EsterasePyuria (the presence of leukocytes in the urine) can be detected using the leukocyte esterase reagentstrip test. The assay is based on the chemi¬cal detection of esterases, which are enzymes containedwithin the azurophilic granules of polymorphonuclear leukocytes. Esterase level is directly proportional tothe number of leukocytes present in a urine sample. The basis of the chemical reaction is the hydrolysisof an ester to form an aromatic alcohol and acid. The aromatic compound combines with a diazoniumsalt to form an azo-dye that changes to purple. Color intensity read at two minutes is proportional to thenumber of granulocytes in a sample. Positive results are reported semiquantitatively as trace, 1+, 2+, or3+. The sensitivity for Multistix reagent strips is 5 cells per high power field (hpf) to 15 cells/hpf whileChemstrip reagent strips have a sensitivity of 20 leukocytes per uL of urine. Because of this relativeinsensitivity, the absence of leukocyte esterase does not rule out urinary tract infection (UTI). A positiveesterase reaction indicates inflammation secondary to UTI or renal disease.Esterase activity from either intact or lysed granulocytes can give a positive result. Lysed granulocytesmay produce apparent discrepancies between positive dipstick results and negative microscopicexaminations. Lympho¬cytes do not produce a positive reaction. Other sources of esterase such aseosinophils, Trichomonas, or epithelial cells in vaginal fluid may give false positive results. Oxidizingagents such as bleach or colored substances can produce false positives.False negative results can be caused by high concentrations of ascorbic acid (vitamin C), albumin orother proteins (>500mg/dL), glucose (>3000 mg/dL), or ketones. Urine with high specific gravity cancause a false negative reaction because enzyme is not as readily released from crenated white bloodcells. These samples should be examined microscopically so as not to miss clinically significant pyuria.WBC clumping may prevent dispersion of leukocyte esterase and cause a false negative result. Outdatedor deteriorated dipsticks are another cause of false-negative results.Doxycycline, gentamicin and some cephalosporins reduce the reactivity of leukocyte esterase andproduce false negative results. Conversely, imipenem, meropenem, and clavulanic acid can cause falsepositive leukocyte esterase reactions.Most studies comparing the sensitivity of nitrite and leukocyte esterase tests compared to urine culturehave demonstrated that leukocyte esterase is a more sensitive indicator of UTI than nitrite.NitriteThe nitrite test is a rapid, indirect method for detec¬ting bacteriuria. The reaction principle is based onbacterial reduction of dietary nitrate, which is normally present in urine, to nitrite, which is notnor¬mally present. Nitrite reacts with para-arsanilic acid on the dipstick to form a diazonium compoundthat reacts with a benoquinoline to form a pink color. Many of the bacteria that cause UTIs have theability to reduce nitrate, including Escherichia coli, Klebsiella, Pseudomonas, Enterobacter, andCitrobacter. The optimal specimen is a freshly voided, first morning urine that has been retained in thebladder a minimum of 4 hours, per¬mitting adequate time for conversion of nitrate into nitrite by thebacterial enzymes. A positive nitrite test result indicates UTI with significant bacteri¬uria. Test
sensitivity has been standardized to correspond to a urine bac¬terial count of 100,000 colony formingunits/mL (CFU/mL). Color intensity is not proportional to the degree of bacteriuria; results are simplyreported as positive or negative.False positive results can be caused by colored substances in the urine (e.g. phenazopyridine) andprolonged specimen storage at room temper¬ature that allows proliferation of contaminating bacteria. Ifuri¬nalysis cannot be done within two hours after collection, specimens should be refrigerated toprevent bacterial growth.False-negative nitrite results can occur even in the presence of signif¬icant bacteriuria due to a numberof possible factors. The causative organisms may lack the reductase enzyme needed to convert nitrateto nitrite. For example, both yeast and gram positive bacteria are reductase negative. Malnourishedpatients and patients receiving intravenous feed¬ing may have insufficient dietary nitrate to promotethe chemical reaction. The duration of urine retention in the bladder may be too short (< 4 hours) tofacilitate nitrate reduction. Previous antimicrobial therapy may inhibit bacterial metabolism. In thepresence of high numbers of bacteria, nitrite may be further reduced to nitrogen, which is not detected.High concentrations of ascorbic acid or urobilinogen can inhibit the chemical reaction. Of course,outdated or deteriorated dipsticks can also yield false-negatives. Microscopic examination of urinesediment or urine culture should be performed, even with negative nitrite, when clinical symptomssuggest UTI.Vitamin C is a strong reducing agent and interferes with a number of dipstick tests. An evaluation of4379 urinalysis specimens from outpatients in a single laboratory revealed that 23% containedmeasurable vitamin C. An oral dose of 100 mg of vitamin C caused falsely negative dipstick tests forblood, glucose and leukocyte esterase in urine samples tested within 4 hours of ingestion. Vitamin Cconsumption is a likely cause of discrepancies between urine dipstick and microscopic analysis.Specific GravityThe specific gravity of a solution is the ratio of the mass per unit volume of the solution to the mass perunit volume of distilled water. It is a relative measure by weight of the amount of dissolved urinarysolutes. All urine contains some solutes and will always have a specific gravity higher than pure water(1.000). Normally, an adult should be able to concentrate the urine to a specific gravity of 1.016 to1.022. A first morning urine with a specific gravity of 1.023 or higher after overnight fluid deprivationindicates normal renal concentrating capacity.The dipstick specific gravity test is based on the apparent pKa change of polyelectrolytes in relation toionic concentration. In the presence of an indicator, colors range from deep blue-green in urine of lowionic concentration through green and yellow-green in urines of increasing ionic concentration.Diabetes mellitus is associated with increased urinary volume and elevated specific gravity due tourinary glucose, which increases the solute content.Diabetes insipidus results in a large urinary volume with low specific gravity. Hyposthenuria means apersistently low urine specific gravity of < 1.007.Renal tubular disease is often manifested early by a loss of concentrating capacity of the kidneys;specific gravity is < 1.018. Later in the disease process, the capacity to dilute the urine is lost and thepatient can only produce isothenuric urine with a fixed specific gravity of 1.010.The kidneys cannot concentrate urine to a specific gravity of >1.035. Specific gravity readings greaterthan 1.035 by refractometer, accompanied by normal specific gravity by reagent strips, usually containhigher molecular weight solutes such as glucose, protein, radiopaque contrast media or drugs. Organiciodides in contrast media such as meglumine diatrizoate (Renograffin, Hypaque) may be seen in theurine sediment for a brief time after injection of the dye. The crystals resemble cholesterol crystals.Reference RangeDipstick reference ranges are summarized in the following table: Analysis Reference Value If positive, reported as: Specific gravity 1.003 - 1.030 Number Blood Negative Small, moderate, large
Ketones Negative Small, moderate, large Glucose Negative 100, 250, 500, 1000, >1000 mg/dL Protein Negative 30, 100, 300, >2000 mg/dL pH 4.5 - 8.0 Number Leukocyte esterase Negative PositiveMicroscopic ExamA microscopic exam is performed if blood, protein, or leukocyte esterase results are abnormal or if amicroscopic exam is specifically requested. The urine is centrifuged and examined microscopically forWBC, RBC, crystals, casts, bacteria and yeast. Both dipstick and microscopic exam should be performedfor patient populations with a high incidence of genitourinary tract disease.Microscopic urinalysis cannot be completely eliminated because multiple clinically significant findings canonly be detected by examining urine sediment directly. For example, a positive dipstick reaction forblood does not distinguish between red cells, hemoglobin, or casts. Likewise, a positive leukocyteesterase reaction does not distinguish between free WBCs that occur in cystitis, from WBC casts that arecharacteristic of pyelonephritis. Microscopy can detect several other clinically significant abnormalitiesthat are not detected by dipsticks including renal tubular epithelial cells and casts, fatty casts, oval fatbodies, crystalline casts, and crystals.Microscopic examination is considered normal if all of the following criteria are met: 0 to 6 erythrocytes per high power field 0 to 6 leukocytes per high power field < 3 hyaline or < 1 granular cast per low power field Absence of any other casts Absence of significant crystals (i.e. cystine, leucine, tyrosine)Specimen RequirementSpecimen requirement is 10 mL from a random urine collection. A first morning void (overnight)specimen is preferred because it is more concentrated and can be assumed to have been in the bladderfor a number of hours. A dilute specimen is more likely to yield a false negative result.Urine should be tested as soon as possible after collection. Some determinations such as urobilinogen,bilirubin and pH are only valid if obtained on a fresh specimen. Other chemistry results will begin tochange within 2 hours at room temperature. Bacterial growth, cellular degradation, precipitation ofamorphous material, and increasing pH due to urease producing bacteria adversely affect proteinmeasurements. A urine more than 24 hours old, even if refrigerated should not be tested. If urine hasbeen refrigerated, it should be allowed to return to room temperature before testing. Refrigeration maycause an increase in specific gravity and precipitation of amorphous phosphates and urates. Glucosesensitivity is adversely affected by not testing at room temperature. Urinary Tract Infection GuidelinesRoutine urine cultures in uncomplicated cystitis have been shown to increase the cost of care by 39%,but decrease duration of symptoms by only 10%. Recently, guidelines have been published concerningthe use of cultures in evaluating female urinary tract infections. In general, young, sexually active,nonpregnant, immunocompetent females without known GU tract abnormalities presenting with recent-onset dysuria, frequency, or urgency and pyuria meet the definition of uncomplicated cystitis. In thissituation, dipstick testing or urine microscopy should be done to establish the presence of pyuria, butpretreatment urine culture is not required. In this setting, the sensitivity of the dipstick leukocyteesterase is 75-96%. A negative dipstick result should be followed by microscopic exam for pyuria. Othercauses of acute dysuria, including chlamydia, gonorrhea, herpes, and candida or trichomonas vaginitisshould by ruled out by history and urinalysis. Urethritis due to chlamydia, gonorrhea, or herpes usuallyalso results in pyuria, while vaginitis due to Candida or Trichomonas usually does not.
While 3 days empiric treatment with Bactrim or a quinolone is suggested for uncomplicated acutecystitis, therapy should be extended to 7 days if symptoms persist more than 7 days, the patient is >65years of age, or there is a history of another recent UTI or diabetes mellitus. In any case, if symptomspersist or relapse occurs within 2 weeks time, urine culture should be done. Pregnant women shouldhave a pre-treatment urine culture and begin empiric therapy with a follow-up urine culture 1-2 weeksafter 7 days of empiric therapy is completed.In summary, in women with typical symptoms, the diagnosis of cystitis can be presumed if pyuria ispresent on leukocyte esterase testing or microscopy. No urine culture is performed and a short course ofempiric antibiotic therapy is given. No follow-up visit or culture after therapy is recommended unlesssymptoms persist or recur. If pyuria is absent or there are atypical clinical features or factors thatsuggest a complicated infection, urine culture should be performed before therapy is started. Urine 24 Hour CollectionMuch confusion exists about the proper way to collect a 24 hour urine specimen. The following protocolis recommended. 24 hour urine specimens should be started Sunday through Thursday. Instruct the patient to empty their bladder on the morning the collection is to start and to discard this urine. Collect all urine excreted during the next 24 hours into the urine collection container provided. If even one urine specimen is missed, the test should be stopped and restarted another morning. Exactly 24 hours after the collection was begun, the patient should empty their bladder for the last time into the container provided. The container should be delivered to the laboratory as soon as possible. Urine CultureSince September 1, 1995, urine cultures have been finalized at 24 hours, instead of 48 hours. In arecent study of urine cultures, all uropathogens including yeast were identified by 24 hours incubation.Cultures with growth at greater than 24 hours were contaminants only. This change should result inimproved turn-around-time and fewer contaminant results for the 18,000 urine cultures processedannually. Specimen requirement is 5.0 mL of random urine from a clean, voided midstream urinecollection, catheter, or suprapubic tap in a screw-capped, sterile container. The specimen may berefrigerated up to 24 hours is unable to forward immediately. Reference value is no growth. If growth is>10 colony forming units per mL, bacteria will only be identified. If growth is >100 colony forming unitsper mL, identification and susceptibility testing will be done. Stool Analysis Test OverviewA stool analysis is a series of tests done on a stool (feces) sample to help diagnose certain conditions affecting thedigestive tract , including infection (such as from parasites, viruses, or bacteria), poor nutrient absorption, or cancer.For a stool analysis, a stool sample is collected in a clean container and then sent for laboratory analysis. Laboratoryanalysis includes microscopic examination, chemical tests, and microbiologic tests. A complete stool analysis includesan examination of the physical characteristics of the stool for color, consistency, weight (volume), shape, odor, and thepresence of mucus. The stool may be examined for hidden (occult) blood, fat, meat fibers, bile, white blood cells, andsugars called reducing substances. The pH of the stool also may be measured.A stool culture is done mainly to identify organisms (such as bacteria) that may be causing an infection.Why It Is DoneStool analysis is done to:
Help diagnose diseases of the digestive tract , liver, and pancreas. Certain enzymes (such as trypsin or elastase) may be evaluated in the stool to help determine how well the pancreas is functioning. Help determine the cause of symptoms affecting the digestive tract, including prolonged diarrhea, bloody diarrhea, an increased amount of gas, nausea, vomiting, loss of appetite, bloating, abdominal pain and cramping, and fever. Screen for colorectal cancer by checking for hidden (occult) blood. Detect the presence of parasites, such as pinworms or Giardia lamblia. Detect and identify certain types of bacteria that can cause disease. This test is called a stool culture and can also be used to detect an infection caused by a fungus or virus. Detect poor absorption of nutrients by the digestive tract (malabsorption syndrome). For this test, all stool is collected over a 72-hour period and then analyzed for the presence of fat and meat fibers. The presence of fat may indicate a malabsorption problem. This test is called a 72-hour stool collection or quantitative fecal fat test.How To PrepareYou will need to avoid certain medications for 1 to 2 weeks before the sample is collected. These medications includeantacids, antidiarrheal medications, antiparasite medications, antibiotics, enemas, and laxatives.Inform your health professional if you have recently had an X-ray test using barium contrast material, such as a bariumenema or upper gastrointestinal series (barium swallow). Barium can interfere with test results.Also inform your health professional if you have traveled in recent weeks or months, especially if you have traveledoutside your native country. Parasites, fungi, viruses, or bacteria from other countries may affect the test.If your stool is being tested for blood, you will need to follow a special diet for 2 days before the stool collection periodbegins. This diet includes small amounts of chicken, turkey, and tuna (no red meat), raw and cooked vegetables andfruits, bran cereals, peanuts, and popcorn. Avoid turnips, cauliflower, broccoli, bananas, cantaloupe, beets, andparsnips, since these foods can cause inaccurate test results. Do not drink any alcoholic beverages or take aspirin orvitamin C for 2 days before the test.How It Is DoneStool samples can be collected at home, in your health professionals office, at a medical clinic, or at the hospital.You may need to collect samples over a period of time from 1 to 3 days. Follow the same procedure for each day.If you collect the samples at home, you will be given stool collection kits to use each day. Each kit contains applicatorsticks and two sterile containers.Collect the samples as follows: Urinate before collecting the stool to avoid contaminating the sample. Put on gloves before handling your stool. Some infectious organisms are contagious while in stool. Wash your hands after you remove your gloves. Pass stool (but no urine) into a dry container. Your health professional may give you a special container for the test. Do not collect the sample from the toilet bowl. Avoid mixing toilet paper, water, or soap with the sample. Using one of the applicator sticks, place a small amount of stool in each of the two containers. Replace the lids and label each with your name, your health professionals name, and the date the stool was collected. Use one kit for each days collection, and collect a sample only once a day unless otherwise directed.Either solid or liquid stool can be collected. Deliver the sealed container within 1 hour to your health professionals officeor directly to a laboratory. Wash your hands well after collecting the sample.If the stool is collected in your health professionals office or the hospital, you will pass the stool in a plastic receptaclethat is inserted under the toilet seat or in a bedpan. Do not urinate while passing the stool. If you have diarrhea, a largeplastic bag taped to the toilet seat may make the collection process easier; the bag is then placed in a plastic container.If you are constipated, you may be given a small enema. The nurse will package the sample for laboratory analysis.If the sample is being tested for quantitative fats, a 72-hour collection period is required. This period starts early in themorning and continues for 3 consecutive days. The stool samples are collected in a large container and refrigerated.
If the sample is being collected because you have digestive symptoms after traveling outside your native country,several samples collected over 7 to 10 days may be needed.In infants and young children, samples may be obtained from diapers (if the stool is not contaminated with urine) or froma small-diameter glass tube inserted into the infants rectum while the baby is held on an adults lap.For certain microbiologic tests, the stool sample is collected by a rectal swab. Commercially prepared sterile swabscontaining a preservative are used. The swab is inserted into the rectum past the anal sphincter, without using alubricant, rotated gently, and then withdrawn. It is placed in a clean, dry container and sent for analysis within 60minutes.Pinworm testA stool analysis may be done to detect pinworms. Although this test may be useful, usually it is not the best way todiagnose pinworms since female pinworms do not lay many eggs in the rectum. A simpler method of detectingpinworms can be done using cellophane tape. Press a piece of cellophane tape, sticky side out, to the anal area. Holdthe tape in place for a few seconds. If pinworms are present, they will stick to the tape. The test should be done early inthe morning before bathing or having a bowel movement. The tape test can be done at home or in your healthprofessionals office.How It FeelsCollecting a stool sample normally does not cause any discomfort. If you are constipated, straining to pass stool may bepainful.If your health professional uses a rectal swab to collect the sample, you may feel some pressure or discomfort as theswab is inserted into your rectum.RisksAny stool sample may contain highly infectious organisms that can spread disease. Thorough hand-washing and carefulhandling techniques are essential to avoid spreading a possible infection from the stool sample.ResultsStool analysis test results usually take at least 1 to 3 days. Stool analysisNormal: The stool appears brown, soft, and well-formed in consistency. No blood, mucus, pus, bacteria, viruses, fungi, or parasites are present in the stool. The shape of the stool is tubular, reflecting its passage through the colon. Normal pH of stool is about 6. Less than 2 milligrams per gram (mg/g) of certain sugars called reducing factors are present in the stool.Abnormal: An increased volume of stool may indicate poor absorption of fats. Blood, mucus, pus, bacteria, viruses, fungi, or parasites are present in the stool. Low levels of certain enzymes (such as trypsin or elastase) may be present. pH is less than 5.3 or greater than 6.8. Reducing factors are greater than 5 mg/g; between 2 and 5 mg/g is considered borderline.Abnormal values High levels of fat in the stool may indicate chronic pancreatitis, sprue (celiac disease), cystic fibrosis, or other disorders that affect the absorption of fats. The presence of undigested meat fibers in the stool may indicate pancreatitis.
A pH greater than 6.8 may indicate poor absorption of carbohydrates or fat and problems with the amount of bile in the digestive tract. Stool with a pH less than 5.3 may indicate poor absorption of sugars. Low levels of certain enzymes (such as trypsin or elastase) may indicate digestive complications of the pancreas or problems from conditions, such as cystic fibrosis. The presence of blood in the stool indicates bleeding in the digestive tract. The presence of white blood cells in the stool may indicate bacterial diarrhea. A specific organism may be identified. Rotaviruses are a common cause of diarrhea in young children. If diarrhea is present, testing may be done to determine whether rotaviruses are present in the stool. High levels of reducing factors in the stool may indicate a problem digesting certain sugars, especially sucrase and lactase. Low levels of reducing factors may occur in sprue (celiac disease), cystic fibrosis, or malnutrition. Medications such as colchicine (for gout) or oral contraceptives may also cause low levels.What Affects the Test Many medications can interfere with test results, including antibiotics, antidiarrheal medications, barium, bismuth, iron, ascorbic acid, aspirin, and magnesium. Some foods can affect certain tests. For example, a diet high in red meat can cause false-positive results in testing for hidden (occult) blood. Stool samples contaminated with urine, menstrual blood, or bleeding hemorrhoids may interfere with results. Bismuth found in toilet paper and paper towels can interfere with test results. Exposing the stool sample to air or room temperature or failing to send the sample to a laboratory within 1 hour of collection may make the sample useless for analysis.What To Think About Stool analysis may be done to check for hidden (occult) blood in the stool. For more information, see the medical test Fecal Occult Blood Test (FOBT). A stool culture is done mainly to identify bacteria that may be causing an infection. Some viruses also can be identified with a stool culture. Other tests can also be used to detect an infection caused by a fungus or parasite. For more information, see the medical test Stool Culture. A bowel transit time test may be done by your health professional to help evaluate the cause of abnormal movement of food through the digestive tract. For more information, see the medical test Bowel Transit Time. The D-xylose absorption test is done to help diagnose problems that prevent the small intestine from absorbing nutrients in food. This test may be done when symptoms of malabsorption syndrome (such as chronic diarrhea, weight loss, and weakness) are present. For more information, see the medical test D- Xylose Absorption Test. Pancreatic function may be normal in some people with cystic fibrosis. For this reason, a stool analysis to measure trypsin or elastase is not as reliable as the sweat test to detect cystic fibrosis. For more information, see the medical test Sweat Test. Stool Culture Test OverviewA stool culture is done to identify bacteria or viruses that may be causing an infection. More than 50 different kinds ofbacteria normally live in the intestines . However, disease can result if large numbers of abnormal organisms(bacteria, viruses, fungi, or parasites) grow in the intestines. Certain types of viruses, fungi, or parasites can beidentified with a stool culture. A stool culture may be done if you have persistent diarrhea.For a stool culture, a stool sample is collected in a clean container and placed under conditions that allow bacteria orother organisms to grow. The type of infection is identified by noting the appearance of the growth, by performingchemical tests on the stool sample, and by looking at the sample under a microscope. If an infection is found, the test ispositive. If there is no organism growth, the test is negative.Usually several stool samples are collected over a period of days for accurate test results.Why It Is Done
A stool culture is done to: Detect and identify certain types of bacteria, viruses, fungi, or parasites that can cause disease. Symptoms of an intestinal disease may include prolonged diarrhea, bloody diarrhea, an increased amount of gas, nausea, vomiting, loss of appetite, bloating, abdominal pain and cramping, and fever. Identify a person who may not have any symptoms of disease but who carries bacteria that can spread to others. This person is called a carrier. A person who is a carrier and who handles food is likely to infect others.Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will bedone, or what the results will indicate. To help you understand the importance of this test, fill out the medical testinformation form (What is a PDF document?).How To PrepareNo special preparation is required before having this test. Do not collect a stool sample if you have bleedinghemorrhoids. Women should not collect a stool sample during their menstrual period; wait until 3 days after your periodhas stopped. If you have recently taken antibiotics, traveled out of your native country, or had a recent test with contrastmaterial, tell your health professional when you receive the stool sample collection container.How It Is DoneThe stool sample for this test may be collected at home. If you are in the hospital, a nurse may help you collect thesample.To collect the sample, you need to: Wear gloves before collecting your specimen. Pass stool (but not urine) into a dry container. You may be given a container that can be placed under the toilet seat. Either solid or liquid stools can be collected. Avoid mixing toilet paper, water, or soap with the sample. Seal the container and label it with your name, your health professionals name, and the date the sample was collected. Wash your hands well after collecting the sample to avoid spreading an infection. Deliver the sealed container as soon as possible to your health professionals office or directly to the lab.Your health professional may collect a stool sample by gently inserting a cotton swab into your rectum if you are unableto pass a stool sample.How It FeelsCollecting a stool sample does not normally cause any discomfort.If your health professional collects the stool sample during a rectal examination, you may feel some pressure ordiscomfort as the cotton swab is inserted into your rectum.RisksThere are no risks associated with collecting a stool sample. It is important to wear gloves before and wash your handswell after collecting the sample so that you do not spread an infection.ResultsA stool culture is done to identify bacteria, viruses, fungi, or parasites that may be causing an infection. Stool culture testresults usually take 2 to 3 days. Stool cultureNormal: No disease-causing (pathogenic) bacteria, viruses, fungi, or parasites are present or grow in the culture.Abnormal: Pathogenic bacteria (such as salmonella, shigella, campylobacter, certain types of Escherichia coli, or Yersinia enterocolitica) grow in the culture. Some of the more common diseases found using a stool culture include food poisoning and pseudomembranous enterocolitis. Fungi or parasites such as Giardia
lamblia are found. Cholera and typhoid fever are less common diseases detected by stool culture.If bacteria are found in the culture, sensitivity testing may be done to determine the best antibiotic to kill the bacteria.What Affects the TestFactors that can interfere with your test and the accuracy of the results include: Recent use of antibiotics, medication (such as bismuth) to control diarrhea, enemas, or laxatives. Recent X-ray tests using a contrast material containing barium. A stool sample contaminated with urine or blood. Delay in getting the stool sample to the lab for testing.What To Think About A stool culture that does not grow any disease-causing (pathogenic) organism may not rule out an infection. Factors such as the amount of stool collected, the type of culture done, and previous use of antibiotics can prevent the growth of an organism in the culture. Sensitivity testing helps the health professional choose the best medication to kill the specific types of bacteria or fungi infecting a person. A test for parasites may be done using a sample of stool. Parasites are neither bacteria nor viruses and include organisms such as worms (pinworms, roundworms, tapeworms) and the protozoan Giardia that causes giardiasis. These parasites commonly infect the intestines. The parasites or their eggs can often be seen during an examination of the stool sample under a microscope. A stool sample can also be checked for the presence of: o White blood cells, which may indicate an infection. If many white blood cells are present but no harmful bacteria grow in the stool culture, other diseases (such as inflammatory bowel disease) may be present. o Blood, which may indicate sores inside the intestines or stomach. o Poisonous substances (toxins) produced by some types of bacteria. A stool analysis is a series of tests done on a sample of stool to help diagnose certain conditions affecting the digestive tract, including infection, poor absorption, or cancer. For more information, see the medical test Stool Analysis. Stool CulturesRoutine stool cultures for bacterial causes of diarrhea detect Campylobacter, Salmonella and Shigella.Special media to detect E. coli O157 should also be included with all stool cultures because of the seriousnature of this pathogen.Campylobacter is the most common bacterial cause of enteritis worldwide, in both developed &developing nations. Campylobacter enteritis can be associated with significant sequelae includingGuillain-Barre syndrome, and can also result in bacteremia. Campylobacter is a fastidious organism &isolation from stool culture is dependent upon prompt receipt of a fresh specimen in the lab. Non-culturedetection methods for Campylobacter antigen by enzyme immunoassay (EIA) are now available anddetect 25% more Campylobacter isolates than culture alone.E. coli O157 produces shiga toxin and is associated with hemorrhagic colitis and hemolytic uremicsyndrome. Relatively recently, many other serotypes of shiga toxin producing E. coli have beendiscovered that cause similar disease. These serotypes appear to be increasing in prevalence and are notdetected by routine stool cultures. Immunoassays for detection of shiga toxin are available that identifymultiple serotypes and increase detection rates by 20-60%.
Fecal Occult Blood Test (FOBT) Test OverviewA fecal occult blood test detects blood in the stool by placing a small sample of stool on a chemically treated card, pad,or wipe; then a chemical developer solution is put on top of the sample. If the card, pad, or cloth turns blue, there isblood in the stool.Fecal occult blood may be done to evaluate some intestinal conditions or to screen for colorectal cancer, which affectsthe large intestine (colon ) and the rectum. In the United States, colorectal cancer is the second leading cause of allcancer deaths. Blood in the stool may be the only symptom of colon cancer. However, not all blood in the stool iscaused by cancer. Other conditions that can cause blood in the stool include: Hemorrhoids, which are enlarged, swollen veins in the anus. Hemorrhoids can occur inside the anus (internal hemorrhoids) or outside of the anus (external hemorrhoids). Anal fissures, which are narrow tears that extends from the muscles that control the anus (anal sphincters) up into the anal canal. Colon polyps: small growths of excess tissue that often grow on a stem or stalk. Peptic ulcers, which are craterlike sores that develop when the digestive juices produced by the stomach eat away or erode the lining of the digestive tract. Ulcerative colitis, a type of inflammatory bowel disease (IBD) that causes inflammation and craterlike sores (ulcers) in the inner lining of the colon and rectum. Gastroesophageal reflux disease (GERD), which is the abnormal backflow (reflux) of food, stomach acid, and other digestive juices into the esophagus. Crohns disease, which is a form of inflammatory bowel disease that causes inflammation and ulcers that may affect the deepest layers of the lining of the digestive tract. Use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs).Although fecal occult blood testing may be used to screen for colorectal cancer, it is never used to diagnose thisdisease. Other screening and diagnostic tests for colon cancer include a digital rectal examination, barium enema,flexible sigmoidoscopy, colonoscopy, or CT scan.Checking for hidden (occult) blood in the stool can be done at home. Testing kits are available at pharmacies without aprescription, or your health professional may order a testing kit for you to use at home. If a home fecal occult blood testdetects blood in your stool, contact your health professional.Health ToolsHealth tools help you make wise health decisions or take action to improve your health.Why It Is DoneA fecal occult blood test (FOBT) is done to: To detect the presence of blood in the stool. Blood in the stool may be caused by hemorrhoids, anal fissure, colon polyps, colorectal cancer, and many other conditions that cause bleeding in the gastrointestinal tract. To screen for cancer of the colon and rectum (colorectal cancer). FOBT is a useful screening tool for colorectal cancer because cancerous tissue and precancerous polyps are more likely to bleed than normal colon tissue. Polyps and cancers appear to grow slowly and they may not bleed all the time. Sometimes blood in the stool is the only symptom of colon cancer. A FOBT increases the chances that bleeding will be detected. Once detected, additional tests can be done to diagnose the cause of the bleeding. It is important to contact your health professional if a home test detects blood in your stool. Home screening for colon cancer does not replace the need for a regular examination by your health professional. To help evaluate the possible cause of abdominal pain. To evaluate the cause of anemia. As part of a routine physical examination for those at increased risk for colon cancer, especially after the age of 50.How To Prepare
Since colon cancers may bleed only intermittently, the test for blood in the stool is done over several days on threedifferent bowel movements. This increases the chance of detecting trace amounts of blood in your stool.To increase the accuracy of the test, you should make some simple diet changes to add roughage to your diet at least 2to 3 days before starting the test and continue until you have collected all three stool samples. Some ways to addroughage to your diet include eating raw and cooked carrots, corn, or spinach; prunes; bran cereals; peanuts; andpopcorn.Before doing a fecal occult blood test (FOBT), avoid the following for 2 to 3 days before the test. Turnips, beets, radishes, horseradish, artichokes, mushrooms, broccoli, bean sprouts, cauliflower, apples, oranges, bananas, grapes, and melon, since these foods can cause the results to be positive for blood when blood is not in the stool (false-positive test results) Red meat, because blood in the meat may cause false test results. Small amounts of chicken, turkey, or fish will not interfere with test results. Iron supplements Aspirin (or products that contain aspirin) and nonsteroidal anti-inflammatory drugs (NSAIDs) Vitamin C supplements Medications, such as colchicine, iodine, antacids, or boric acidDo not perform the test during your menstrual period or if you have active bleeding caused by hemorrhoids. Also, do nottest a stool sample that has been in contact with toilet bowl cleaning products that turn the water blue.Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will bedone, or what the results will indicate. To help you understand the importance of this test, fill out the medical testinformation form (What is a PDF document?).How It Is DoneThe procedure for testing blood in the stool varies depending upon the type of home test you have. It is important tofollow the manufacturers instructions provided with any test. For most tests, you will use stool samples from threedifferent bowel movements over three different days.General instructionsFor any home diagnostic test, follow these general guidelines: Check the expiration date on the package. Do not use a test kit after its expiration date. The chemicals in the kit may not work properly after that date. Store the test kit as directed. Many kits need to be stored in a refrigerator or cool place. Read the instructions that come with your test carefully and thoroughly before doing the test. Pay attention to any special preparations you need to take before doing the test, such as avoiding certain foods or limiting your physical activity. Follow the directions exactly. Do all the steps, in order, without skipping any of them. If a step in the test needs to be timed, use a watch. Do not guess at the timing. If you are color-blind or have trouble distinguishing colors, have someone else read the test results for you. Most test results depend on being able to see color changes on a test strip. Record the results of the test so you can discuss them with your health professional.The following directions are for one of the most common tests used to detect blood in the stool.Stool guaiac cards Complete the identification information on the front of each card. During a bowel movement, collect a small amount of stool on one end of an applicator. You might try catching the stool on some plastic wrap draped loosely over the toilet bowl and held in place by the toilet seat. If you use a container to collect the stool, first clean and rinse it well to get rid of any substance that may affect the test results. Apply a thin smear of stool inside box A. Reuse the same applicator to obtain a second sample from a different part of the stool. Apply a thin smear inside box B. Close the cover of the slide. Complete the remaining two cards in the same way during two other bowel movements.
You probably will be instructed to return all slides to your health professional either in person or by mail within 4 days of collecting the samples. If you have the developer solution, wait 3 to 5 minutes before you apply 1 drop of the developer solution to the area containing stool. Apply 1 drop of the developer solution to the control areas of the card so that you will know what positive and negative test results should look like. An area to read the results is found on the reverse side of the card. Turn the card over and read the results within 10 seconds.Other test kits A kit that uses a special cloth to wipe after a bowel movement can also be used. After wiping with the cloth, the developer solution is put on the cloth to check for color change that indicates blood in the stool. A special test pad placed in the toilet will change color when a stool with blood interacts with the pad.If you find blood in your stool, contact your health professional as soon as possible.How It FeelsYou may find it unpleasant to collect a stool sample for a fecal occult blood test (FOBT).RisksThere are no risks associated with doing a fecal occult blood test (FOBT).ResultsA fecal occult blood test (FOBT) detects blood in the stool by placing a small sample of stool on a chemically treatedcard, pad, or wipe; then a chemical developer solution is put on top of the sample. If the card, pad, or wipe turns blue,there is blood in the stool. The way results are displayed may vary depending on the type of test you are using. If youare given stool guaiac cards by your health professional, you may not be able read the results yourself. Instead, you willreturn the cards to your health professional, who will then develop them. Fecal occult blood testing Normal: A normal test (no color change) indicates that at the time you collected your stool samples there was no detectable blood in your stool. Normal test results are called negative. Abnormal: An abnormal test (blue color change) may indicate that at the time of the test there was detectable blood in the stool. Abnormal test results are called positive.Normal resultsA negative test result does not rule out the possibility of colon cancer or colon polyps. FOBT is positive in only 30% to50% of the people who have colon cancer. Discuss with your health professional how often you should have an FOBTdepending on your age and any risk factors you may have for colon cancer.Abnormal resultsIf you have a positive test result, it may be caused by something other than colon polyps or colon cancer. Blood in your stool may be caused by red meat you have eaten, menstrual bleeding, hemorrhoids, Crohns disease, ulcerative colitis, a stomach ulcer, or the use of aspirin or nonsteroidal anti- inflammatory drugs (NSAIDs). If you do not haverisk factors for colon polyps or colon cancer, your health professional may want you to repeat the FOBT. If the repeat test is negative, you may resume regular FOBT screening. If the repeat test is positive, you may have further testing, such as endoscopy, colonoscopy, barium enema, or flexible sigmoidoscopy. If blood in the stool could be caused by red meat you have eaten, menstrual bleeding, hemorrhoids, Crohns disease, ulcerative colitis, or a stomach ulcer and you have risk factors for colon polyps or colon cancer, your health professional may recommend further testing, such as colonoscopy, barium enema, or flexible sigmoidoscopy, without doing another FOBT.
A positive test result may be caused by a polyp, a precancerous polyp, or cancer. With a positive result, there is about a5% to 10% probability that you have early-stage colon cancer. About 50% of the time there is no abnormality found thatcan explain the positive FOBT result.If you have a positive test result and you: Are younger than 50, and you do not have risk factors for colon polyps or colon cancer, your health professional may want you to repeat the FOBT. If the repeat test is negative, you may resume regular FOBT screening. If the repeat test is positive, you may need further testing, such as colonoscopy, barium enema, or flexible sigmoidoscopy. Are older than 50, and you have not been evaluated recently for colon polyps, colon cancer, Crohns disease, ulcerative colitis, or stomach ulcers, you will probably need further testing, such as upper gastrointestinal endoscopy, colonoscopy, barium enema, or flexible sigmoidoscopy. Have been evaluated recently for colon polyps, colon cancer, Crohns disease, ulcerative colitis, or stomach ulcers, your health professional may simply have you repeat the FOBT or you may resume regular FOBT screening.What Affects the TestFactors that can interfere with your test and the accuracy of the results include: Medications, such as aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), anticoagulants, or corticosteroids. The use of laxatives, vitamin C, or iron supplements. Blood in the urine, menstrual bleeding, hemorrhoids, an anal fissure, bleeding gums, nosebleeds, or eating certain vegetables (radishes, turnips or beets) or red meat cooked rare within 2 days before the test, which can cause a false-positive test result. The use of a product to clean or deodorize the toilet that contaminates the stool sample.What To Think About A fecal occult blood test (FOBT) is most often used as a screening tool. By itself, an FOBT cannot be used to diagnose colon polyps or colon cancer. If an FOBT detects blood in the stool, you may need additional tests, such as a rectal exam, colonoscopy, barium enema, endoscopy, or flexible sigmoidoscopy. For more information, see the medical tests Digital Rectal Examination (DRE), Colonoscopy, Barium Enema, Upper Gastrointestinal Endoscopy, Sigmoidoscopy (Anoscopy, Proctoscopy), and Computed Tomography (CT) Scan. An FOBT has a high rate of false-positive results. This means that the test may be positive when you do not actually have a polyp or cancer. This can occur either because the blood is coming from another source, such as from hemorrhoids, or because the test falsely detected blood. Further testing, such as a colonoscopy, may be done to determine the cause of the positive FOBT results and to rule out serious disease, such as cancer. People ages 50 to 80 who have an FOBT every 1 to 2 years are up to 33% less likely to die of colorectal cancer than people who do not have regular FOBTs. Medical experts disagree about routine screening for colorectal cancer. Talk to your health professional about your risk factors and which testing is best for you.Credits Author Jan Nissl, RN, BS Editor Susan Van Houten, RN, BSN, MBA Associate Editor Tracy Landauer
Fecal Occult Blood Test (FOBT) Colorectal cancer is the only major cancer that affects men and women almost equally. It is rare inpersons under age 40, but the incidence begins to rise substantially after age 50. About 6% of peopledevelop colorectal cancer by 80 years of age and 50% die as a result of the cancer. Three recentrandomized, controlled trials have convincingly shown that the mortality rate can be reduced 15 to 35%by screening with fecal occult blood tests (FOBT). As a result of these studies, major professionalorganizations such as the American Cancer Society, the United States Preventative Service Task Force,the American College of Physicians, and the College of American Pathologists now recommend annualtesting of all adults at 50 years of age or older. FOBT was also added to the list of approved MedicarePreventive Service Benefits on January 1, 1998.Current guidelines recommend screening with a guaiac-based test such as Hemoccult II, which has beenclassified as a waived test by CLIA 88. Guaiac based FOBT make use of the pseudoperoxidase activity ofhemoglobin. Guaiac turns blue after oxidation by oxidants or peroxidases in the presence of an oxygendonor such as hydrogen peroxide. The likelihood that a guaiac-based test will be positive is proportionalto the quantity of fecal heme, which in turn is related to the size and location of the bleeding lesion.FOBT are optimally designed to detect large, distal lesions. Generally, 10 mL of daily blood loss isrequired for Hemocult II tests to be positive 50% of the time.Patients should collect a total of six samples in order to compensate for sampling error since blood is notevenly distributed in stool. Two slides should be prepared from each of three consecutive bowelmovements. The collection should be made 24 to 48 hours after eating a meat free diet and avoidanceof vitamin C, aspirin, and nonsteroidal anti-inflammatory drugs. Slides need to be developed within 7days of collection. Longer periods of storage cause weakly positive stools to become falsely negative.The dried stool specimens should not be rehydrated with a drop of water at the time of developmentbecause this practice increases the false positive rate up to 16%. A false positive rate of this magnitudeleads to too many nonproductive colonoscopic examinations and makes screening impractical.FOBT is considered positive if even one of the six slide windows turns blue. A middle-aged adult with apositive result on an initial FOBT (performed without slide rehydration) has a 7 to 14% probability ofearly colorectal cancer (Dukes stage A or B). The probability of early cancer or a large (>1 cm) adenomais approximately 30%. Cancer detection rates are lower following rescreening. Nonetheless, cancerdetection rates are high enough to warrant a complete evaluation of the colon and rectum whenever aperson has a positive test either initially or at rescreening. If the results of colonoscopy are negative,FOBT does not need to be repeated for 5 years. If colonoscopy reveals cancer or a high-risk adenoma,periodic colonoscopic surveillance is indicated.A negative result on FOBT does not rule out colorectal cancer, because the sensitivity of the test is only30 to 50%. FOBT should be repeated either annually or biennially. If symptoms develop that suggestcolorectal cancer a more definitive test should be performed to rule out a neoplasm.Antacids and anti-diarrheal medications containing bismuth render the stool dark and may confound thereading of FOBT. Oral iron supplements give the stool a dark-green or black appearance that may beconfused with the blue color of a positive guaiac test.
Diabetes Mellitus ManagementDiabetes mellitus is a chronic illness that requires continuing medical care and education to preventacute complications and reduce the risk of chronic complications such as retinopathy, nephropathy, andneuropathy. The Diabetes Control and Complications Trial (DCCT) demonstrated that in patients withtype 1 diabetes the risk of developing these complications was reduced 50 to 75% by intensivetreatment regimens that decreased the average hemoglobin A1c level to 7.2%. The reduction in risk ofthese complications correlated continuously with the reduction in hemoglobin A1c levels, implying thatcomplete normalization of glycemia levels may prevent complications.In view of the DCCTs findings, the American Diabetes Association has recommended the following goalsfor glycemic control in patients with type 1 diabetes. Similar goals have been recommended for patientswith type 2 diabetes. The targets should be adjusted in patients with a history of hypoglycemia. Biochemical Index Nondiabetic Diabetic Goal Action suggested Preprandial glucose <115 mg/dL 80 - 120 mg/dL <80 or >140 Bedtime glucose <120 mg/dL 100 - 140 mg/dL <100 or >160 Hemoglobin A1c <6% <7% >8%Initial Patient VisitDuring the initial visit, laboratory tests should be performed to establish the diagnosis of diabetesmellitus, determine the degree of past and present glycemic control, and determine the presence orabsence of chronic complications and risk factors. Recommended tests include: Fasting plasma glucose ( random plasma glucose may be obtained in an undiagnosed symptomatic patient for diagnosis) Glycated hemoglobin Fasting lipid profile including cholesterol, HDL cholesterol, LDL cholesterol, & triglycerides in adults and children older than 2 years Serum creatinine in adults and children with proteinuria Urinalysis including glucose, ketones, protein, and sediment Urine culture if the sediment is abnormal or patient is symptomatic Urine microalbumin for postpubertal patients with diabetes for at least 5 years and all patients with type 2 diabetes (timed specimen or albumin/creatinine ratio) Thyroid function tests when clinically indicatedPatients should be instructed in self monitoring of blood glucose and urine ketones and the use of arecord system. The frequency of blood glucose monitoring should be individualized according to theseverity of illness, treatment plan, and response to treatment.Continuing CarePeriodic follow-up tests play an essential part in the continuing management of every patient withdiabetes. Recommended tests and the suggested frequency of testing are summarized in the followingtable. Laboratory Patient Population Frequency of Testing Test HbA1c Stable glycemic control At least 1 to 2 times per year Poor control or changed therapy Quarterly Lipid profile Initial profile abnormal Annually Treatment for dyslipidemia As needed to monitor therapy