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Preanalytical variables and errors in sampling

This document discusses a study on pre-analytical variables and errors that can affect laboratory test outcomes in hospitals and diagnostic labs. It highlights controllable and uncontrollable factors that lead to unexpected test results, emphasizing the need for quality control and effective specimen handling to improve diagnostic accuracy. The study aims to identify significant pre-analytical errors and propose preventive measures to enhance patient safety and reliability of laboratory results.

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TITLE: A study of the Pre analytical variables and errors in sample collection, sample transport, sample preparation and storage. INTRODUCTION: Thousands of routine biochemical analytes are estimated in sera/plasma/whole blood/urine/sputum on a day-to-day basis in hospitals/diagnostic labs. Hence, pre-analytical variables and errors become imperative in determining test outcomes, patient diagnosis and treatment/therapy. Many clinicians tend to think that diseases are the only possible cause of abnormal test results. In practice, though, there are factors apart from pathologic conditions responsible for unexpected/grossly deviant test results. Therefore, wherever possible, preanalytical variability should be controlled so that the correct clinical interpretation of the disease process can be made. Variables can be Controllable and Uncontrollable. Controllable variables include posture, prolonged bed rest, exercise, physical training and circadian variation. Others relate to diet, obesity, allergies to certain disinfectants used at venipuncture sites, Tourniquet application (efficiency of handler). Common errors relate to inadequate knowledge on part of the phlebotomist/technologist, laxity in handling, time delays in transportation, improper patient identification, sample mix-up, inefficient separation and storage of specimens, improper phlebotomy techniques. Patient Identification errors are rampant. They refer mostly to unlabeled/wrongly labelled tubes. Timing of Collection becomes significant in certain cases-Basal State/fasting draw, specimens affected by Time of Draw viz Cortisol, Timed Draws, Therapeutic Drug Monitoring. Test Collection Errors relate to Site of Draw-Vein/Capillary/Artery; warming and disinfection prior to collection. Transport-Some specimens eg. ABG must be transported immediately after collection; specimens for Serum/Plasma Chemistry testing must be separated and centrifuged within 2 hrs. a delay might prove expensive. Temp. Of Specimen & Transport Container also matter. Whether leak proof plastic bags/open vials are used for transportation might affect test results. Some specimens eg. Bilirubin is to be protected from sunlight. It is always favourable to avoid extremes of temperature. Phlebotomy errors may harm the patient (as in venipuncture) or result in needle-stick injuries to the phlebotomist. A Survey-Analysis, Questionnaire and Observation model was followed for the project in question. The above mentioned issues are some of the questions this project seeks to answer. This would go a long way in implementation of check measures to reduce future errors and variables, make diagnosis as well as treatment more safe, reliable and accurate. REVIEW OF LITERATURE: The accuracy of test results is dependent on the quality of specimens. Valid lab results require proper specimen collection procedures. Errors at any stage of collection process can lead to serious patient misdiagnosis. Errors during collection are not inevitable and can be prevented by diligent application of quality control, continuing education and effective collection systems.
Types of collection errors-Patient identification, Phlebotomy technique, test collection procedures, specimen transport, specimen processing. Patient identification errors relate to non-tallying numbers in the medical book and the master chart, sample tubes unlabeled, sample tubes labelled insufficiently/incorrectly, collection tubes not labelled at the time of collection, collection tubes labelled by someone other than phlebotomist. Phlebotomy technique errors-Wrong selection of venipuncture site, tourniquet application, improper cleansing of site, improper collection system, too superficial or deep venous access. Test collection errors- Order of draw-affects quality of sample and may lead to erroneous results due to contamination with additive from the previous collection tube. Haemolysis-insufficient collection, collection from area with hematoma, vigorous shaking of tube after collection, milking the site when collecting capillary sample and collecting blood with a small bore needle. Causes of Haemolysis Effects Drawing through vascular access device K Excessive probing NH3 Small needle size LDH Improper needle placement AST Excessive pulling pressure on plunger of syringe ALT Vigorous specimen mixing P, Mg Improper blood and anticoagulant ratio RBC, HCT Test collection errors-Timing of collection-Timed draws, therapeutic drug monitoring General criteria for unacceptable specimen-Haemolysis, lipemia, insufficient quantity, improper preservative, unlabeled specimen, improper specimen collection, improper patient preparation Transport errors-a) Temp.-ABGs, ammonia on ice; cryoglobulins at 37degree C b) Transport containers-leak proof plastic bags in rigid, lockable containers; bilirubin samples to be protected from light. Contrary to what many physicians think, diseases are not the only cause of abnormal test results. The variability due biological factors is often greater than the analytical factors. Variables can be: a) Controllable Posture-the decrease in plasma volume that occurs with the postural change from the supine position to standing results in an increase in the concentration of all proteins, including enzymes and protein hormones Physical Training: Athletes generally have a higher activity of serum enzymes of skeletal muscle origin as
compared to the untrained individual of the same age/sex group. Serum levels of urea, creatinine, and uric acid are higher in athletes. (increased muscle mass) .Athletes have low LDL cholesterol, decreased total lipids. Dietary Habits & Meal: A change from a normal diet to that of a high protein diet causes doubling of plasma urea. Serum cholesterol, uric acid and phosphate concentration are also increased. The physiological effects of meal include increase in blood glucose concentration , Total lipid & ALP. Alcohol, Drugs, Fever, Trauma, Transfusion etc. b) Uncontrollable- Age-In men, serum phosphorus decreases markedly after 20 yrs. of age. Serum total cholesterol and TG increase in both sexes at a rate of 2mg/dl per year to a max. between 50 to 60 years. Gender-Concentration of albumin, calcium, magnesium is higher in men than in women. Haemoglobin concentration is lower in women and hence, serum bilirubin is also slightly low as bilirubin is a degradation product of haemoglobin. Lifestyle-Serum cholesterol, TG, lipoproteins are positively correlated with obesity. (As described in the Laboratory Manual of the Armed Forces Medical Services, India) Because of these factors, there may be a wide difference between expected and actual outcomes, which is often attributed to procedural error. Knowledge of such preanalytical variables will help in understanding the cause of the disparity and hence, lead to more precision and accuracy in reporting. AIMS and OBJECTIVES: -To identify the significant pre analytical errors that occur during specimen collection and transport. -To explain the various means of pre analytical error prevention. -to list the proactive steps to reduce potential preanalytical errors associated with blood/sample collection, transport and handling. METHODOLOGY: Type-Prospective, Descriptive Procedures involved-observation and study of the practice of sample collection in a tertiary care phlebotomy centre(Civil OPD phlebotomy centre, Southern Command Hospital,Pune) and in an acute medical ward(ICU);visits to sample collection ,preparation and storage areas(Dept. of Biochemistry, AFMC, Pune), interaction with phlebotomists/sample collectors and handlers, transporters (Technicians, nursing assistants etc.) and patients. Time (Survey)-6 weeks Time (Analysis)-2 weeks Total Duration of Study-8 weeks SAMPLE SIZE-Total no. Of patients in 6 weeks of study
Observations made at the collection centre-Skill/efficiency of phlebotomists, their knowledge about the job (if adequate), method of collection. The practices in sample collection, preparation, transportation and storage were assessed according to a checklist/questionnaire prepared. Observations & Results These observations were made and the questionnaire conducted at Civil OPD Collection Centre, Southern Command Hospital; Service OPD, ICU-Surgical, and ICU-Medical (wards). At the phlebotomy centre, the technicians and other staff were subjected to the following questionnaire and their response was recorded as below: Questionnaire: Objective: To learn whether the STANDARD OPERATING PROCEDURE as accepted internationally is being followed. What is the procedure followed here for blood/sample collection? -Blood is drawn through a BD Vacutainer/Syringe into the earmarked collection tube after a tourniquet has been tied and the patient has clenched his/her fist. What is the type of blood collection device used? -A BD Vacutainer is the device of choice for most collections, especially by the newer staff. Syringes are preferred in paediatric cases and for obese individuals and also by the older phlebotomists. Objective: To discern various Phlebotomy errors What do you do to ensure minimum trauma to the patient? - SOP on venipuncture is sought to be followed as far as practicable, with emphasis on proper site selection and an attempt is made to finish the draw in a single draw if possible. What do you do to ensure minimum potential for phlebotomist injury? -Phlebotomists wear gloves for every draw compulsorily, which are changed every 3-4 draws. Thus, Needle- Stick injuries can be avoided. As a precaution against accidental contact with patient’s body fluids, the phlebotomist applies a disinfectant (methylated spirit) on his hands before wearing gloves. What do you do to reduce recollections? -We select the right vein if possible, to minimize needle punctures, try to label the tubes correctly and stack up with the right sample reports. We ask the patient to flex his/her arm and clench the fist to ensure pressure equalization and to make the veins prominent. What do you do to ensure test result validity? -We lay stress on the correct SOP for sample collection, proper labelling of tubes, ensuring that the correct analytes go into the correct tubes, etc.
Objective: Patient safety and prevention of complications How important is the site selection for phlebotomy? -Site selection is important to ensure optimal collection of blood, minimize patient trauma by preventing unnecessary needle pricks and also minimize chances of needle stick injuries to the phlebotomists. Do you avoid sites with IV? -Yes, IV sites are to be avoided unless absolutely essential. Do you use alternative arm or draw below the IV to avoid contamination/dilution from IV? -We use the alternative arm preferably; drawing below the IV is possible but rarely used in this centre. Do you close the IV drip for two minutes and then withdraw sample if you cannot avoid the IV site? -Yes, but such cases are pretty rare in the Civil OPD collection centre, more common in the ICU (burns cases). What about cases of Mastectomy-Do you avoid the site (due to lymph stasis)? -Yes, but we do not encounter many such cases in this collection centre. What do you do to minimize infection risk? -Sterilize/Disinfect with alcohol swabs prior to pricking, phlebotomists use latex gloves (high quality), post collection the needles are disposed off in sodium hypobromite solution after destroying in a needle destroyer. What do you do to prevent alteration in body fluids and blood? -No such step is taken. Do you avoid oedematous areas when performing phlebotomies due to accumulation of body fluids? -Yes, preferrably as oedematous areas are difficult sites for venous localisation. How do you take care of possible contamination/dilution of specimen? -Specimens are collected in the specified tubes (colour coded) which are then sealed, leaving minimum room for error. Objective-Venous access difficulties What do you do about obstructed, hardened, scarred veins? -Search for an alternate vein for draw. How difficult is it to locate the right vein? (especially in obese and old, emaciated individuals) -Pretty difficult as in obese individuals, fat interferes in making the vein prominent .In old, emaciated persons; there is always a chance for prick injury.
What alternative sites can we use? (To check their knowledge about alternative draw sites such as top of hand/side of wrist) -Top of hand is commonly used here for children (especially <5yrs), side of wrist is also used if cubital region is inaccessible. What are the areas to be avoided? -IV sites, oedematous areas, sites with injury, etc. What precautions do you take to avoid vein collapse? -Once the needle is inside the vein, attach the BD vacutainer tube to it; let blood flow under the effect of suction created by vacuum. Do not try to force out blood as this might lead to haemolysis/vein collapse. What is the type of blood collection device used? -BD vacutainer in most cases, Syringe is mostly used for children <5 yrs. And in cases where vacuum draw fails. What is the size of the needle used and whether this conforms to the standard bore sizes? -BD vacutainer 21G x 1.5” Syringe 0.56 x 25 mm How do you destroy the used syringe /blood collection device? -The needle is put destroyed by a needle destroyer and then disposed off in Na Hypobromite solution. The vacutainer is disposed off in the earmarked disposal bin that conforms to Biomedical Waste management standards. What are the types of collection tubes used? -We collect blood in the appropriate tubes: Colour marked for different anticoagulants – Purple (EDTA) for ESR, TLC, DLC, Hb Grey (Citrate/Na F)-PTTK Yellow and Red – (without anticoagulant) for LFT, RFT, Bilirubin, lipid profile Objective-To discern whether the proper method of tourniquet application is followed in practice How long is the tourniquet left tied? -up to 1 min. Where do you tie the tourniquet? -Around the elbow Do you ask your patient to clench his fist often? -The patient is asked to clench his fist before the draw and flex his arm 3-4 times to ensure pressure equalization and to make the veins prominent for a suitable collection. Objective-To note the causes for occurrence of test collection errors
What is the duration between sample collection and sample reception at lab? -Approximately 4 hrs. Collection stars at 8 a.m. while the whole day’s quota of samples is sent to the BIOCHEM. LAB. at 12 noon. What precautions are taken during timed draws? -Timed draws are not done here owing to patient overload and staff shortage. How are specimens affected by the time of the day? -Diurnal variations and circadian rhythms affect test results. Growth Hormone peaks in the morning before waking and decreases throughout the day. Serum iron levels change as much as 30 to 50% from morning until evening. Objective-To determine variables to be accounted for in test results What instruction is given to the patient before collection? (with regard to the following parameters) -Diet (fasting/basal state) In general, specimens for determining body constituents should be collected when the patient is in a basal state (in the early morning after awakening and 12-14 hrs. after last ingestion of food.) Fasting /diet restrictions, viz. low fat diet are explained in detail, especially to overanxious elderly patients or their caregivers. Patients should be informed that fasting does not involve abstaining from water. Dehydration might alter test results. For e.g. patients are given clear instructions before a Fasting/PP glucose test or a lipid profile. -Exercise Moderate exercise can cause an increase in blood glucose, lactic acid, serum proteins and creatine kinase. -How the test results might be influenced by disinfectants (allergic reactions)? Hypersensitivity type III may result in serum sickness, type I in anaphylactic shock etc. giving improper test results. Objectives-To understand how containers used for storage and transport might affect test results and to what extent What type of collection vials (sealed/open) do you commonly use? -Sealed vials are used on a daily basis. Are the transport containers leak proof? -Yes, a closed container is used for transportation. Do the cells Rouleaux/marginate/stick to bag/agglutinate enroute? -Such cases do occur inspite of the best precautions. How are the samples protected from sunlight/U.V.radiations? (Bilirubin specifically)
-Samples are transported in sealed vials in a closed container to protect from sunlight/U.V. radiations. However, there is no system to prevent sample alteration due to U.V. ray exposure in the phlebotomy centre as samples remain so for upto 4 hrs. Whether or not the containers are filled completely/adequately? -Yes, in fact there appears to be a shortage of containers and in overloading, sometimes the container lid is not closed. How does specimen dilution account for altered test results? -Excessive anticoagulant relative to sample will cause diluted sample, while less of it will cause agglutination in part of the sample. Objective-To understand various kinds of Transportation Errors Are the specimens transported in proper containers? -Yes, specimens are transported in closed containers that are leak proof and protect against vagaries of nature. How is the quality of sample ensured enroute to the lab from the collection centre? -Not much is done except for ensuring proper sealing of vials and a proper container in transit. Is the whole day’s quota of specimens transported together? -No, the whole day’s quota comes in 2 batches -one at 10:30a.m. and another at 12:30 p.m. Are specimens transported with regard to perishability/need for immediate analysis? (e.g. Arterial Blood Gases) -No How much time has elapsed between sample collection and centrifugation/storage? -up to 3-3 ½ HRS. How are temperature variables accounted for in transportation? -Samples are transported in sealed containers to avoid direct exposure to sun (heat) or cold (as in winter), but nothing is done to make internal temperature constant boxes as this technology is expensive. Any special precautions if taken for say cryoglobulins/ammonia? -No What is the fate of haemolysed/lipemic samples? -Such samples are discarded and a repeat testing is ordered. Objective-What are the major causes of Patient misidentification? Are collection bags labelled correctly? -Yes, in most cases, though occasional errors do occur. What are the steps taken to prevent sample mix-ups?
-Proper labelling of vials, filing of reports along with correct vials in shelves. Do the requisition forms contain all the details including relevant clinical details of the patient? -Yes What criteria are followed for sample rejection? -Haemolysis/Chylasing of samples, inadequacy of sample, lipemic samples, excessive clotting etc. Objective-To understand how significantly these errors and variables affect diagnosis and subsequent treatment -Interaction with the doctor concerned Objective-To understand how to prevent errors best and improve accuracy of test results. What are the steps to be taken towards mechanical error prevention? -Use of a BD vacutainer, conforming to standard bore sizes for needles, following the proper method of tourniquet application, selecting proper site of draw, collection in proper tubes, correct labelling etc. What technology do we use to prevent human error? -Not much of mechanisation is followed, a computerised database of patient data is lacking. What systems does our hospital use to prevent errors by non-laboratory staff collecting blood? -Use of gloves, following SOPs, flexing patient’s arm, BD vacutainers, correct labelling etc. What pro-active implements would reduce the number of preanalytical errors? -More mechanisation in phlebotomy would be desirable. What steps should be undertaken to account for preanalytical variables? -Proper patient counselling regarding diet, exercise, lifestyle etc. PHLEBOTOMY CENTRE DATA Dates-month of July 01 - Jul 02 - Jul 03 - Jul 04 - Jul 05 - Jul 06 - Jul 07 - Jul 08 - Jul 09 - Jul 10 - Jul 11 - Jul 12 - Jul 13 - Jul 14 - Jul 15 - Jul No. of obese patients 3 4 2 3 3 2 2 2 2 4 3 2 3 3 4 No. of old patients 3 3 4 3 4 3 2 5 4 3 2 2 2 1 2 No. of patients in whom venous localization is difficult 4 5 3 4 3 2 2 4 3 3 3 2 2 2 3 No. of tourniquet application errors 1 1 1
No. of collections done with syringes 2 1 2 2 1 2 1 2 3 3 2 1 2 2 3 No. of cases of excessive pressure application 1 1 1 2 No. of double pricks 1 2 1 1 1 2 No. of triple pricks 1 No. of collections done in wrong tubes 1 1 1 1 No. of labelling errors 1 1 No. of cases of wrong sample-reporting slip match 1 1 1 No. of samples haemolysed 1 1 3 1 No. of suspected wrong draws 2 2 1 2 3 2 1 1 2 No. of actual wrong draws as confirmed on lab analysis 1 1 1 1 1 1 15 draws were observed daily at Phlebotomy centre, Civil OPD, Southern Command Hospital, Pune, ICU (Med. and Surg.) and Dept. of Biochemistry, AFMC, Pune. Dates- month of July 16 - Jul 17 - Jul 18 - Jul 19 - Jul 20 - Jul 21 - Jul 22 - Jul 23 - Jul 24 - Jul 25 - Jul 26 - Jul 27 - Jul 28 - Jul 29 - Jul 30 - Jul 31 - Jul No. of obese patients 3 3 4 3 3 4 3 3 4 3 3 3 2 3 3 3 No. of old patients 4 3 2 3 2 3 2 3 2 2 3 2 4 4 3 2 No. of patients in whom venous localization is difficult 3 3 4 2 2 2 2 3 3 2 3 2 3 4 3 No. of tourniquet application errors 1 1 1 No. of collections done with syringes 2 2 2 1 2 1 2 2 3 1 3 2 2 3 2 No. of cases of excessive pressure application 1 1 1 1 2
No. of double pricks 1 1 1 No. of triple pricks 1 No. of collections done in wrong tubes 1 1 1 No. of labelling errors 1 2 1 No. of cases of wrong sample- reporting slip match 1 1 No. of samples haemolyse d 1 1 1 No. of suspected wrong draws 3 2 2 2 1 2 2 3 3 2 2 2 3 3 2 2 No. of actual wrong draws as confirmed on lab analysis 1 1 1 2 1 1 1 15 draws were observed daily at Phlebotomy centre, Civil OPD, Southern Command Hospital, Pune, ICU (Med. and Surg.) and Dept. of Biochemistry, AFMC, Pune. Dates- month of Aug 01- Aug 02- Aug 03- Aug 04- Aug 05- Aug 06- Aug 08- Aug 09- Aug 10- Aug 11- Aug 12- Aug 13- Aug 16- Aug No. of obese patients 4 3 4 2 3 3 2 1 3 2 4 5 1 No. of old patients 4 2 4 3 3 4 2 3 2 5 2 3 3 No. of patients in 3 4 4 5 4 3 4 5 4 5 3 2 4
whom venous localization is difficult No. of tourniquet application errors 1 1 1 1 2 No. of collections done with syringes 3 2 1 2 1 2 2 1 2 1 2 2 No. of cases of excessive pressure application 1 1 1 1 No. of double pricks 1 1 1 No. of triple pricks 1 No. of collections done in wrong tubes 1 2 2 No. of labelling errors 1 1 2 1 1 No. of cases of wrong sample- reporting slip match 1 1 No. of samples haemolysed 1 2 No. of suspected wrong draws 3 2 2 3 2 3 3 4 2 1 2 2 3 No. of actual wrong draws as confirmed on lab analysis 1 1 2 1 2 1 1
15 draws per day were observed at the Civil OPD and ICU surgical collection sites. Some draws were also observed at the phlebotomy room in the Dept. of Biochemistry, AFMC, Pune. The table shows that the no. of old and obese patients and those in which venous localization is difficult is pretty common, as much as a minimum of 15-20%.However,it also tells that venous localization need not be difficult in every elderly, obese patient and children/infants. Use of syringes for collection instead of B.D. vacutainer and application of excess pressure leading to haemolysis is a major source of error. Labelling errors do occur, though not major and occasional wrong patient identification also forms a small fraction of error. Sample haemolysis at the phlebotomy centre does occur sometimes, but double and triple pricks are not too common, which is good to prevent needle stick injury to the phlebotomist and minimize infection risk. General skill of phlebotomists would be rated satisfactory because there is a big disparity between no. of suspected wrong draws and no. of actual wrong draws as found on lab analysis. No. of Old patients 130 19.8 No. of patients in whom venous localization is difficult 142 21.08 No. of tourniquet application errors 12 1.85 No. of collections done with syringes 81 12 No. of cases of excessive pressure application 15 2.23 No. of Double pricks 14 2.2 No. of Triple pricks 4 0.6 No. of collections done in wrong tubes 12 1.85 No. of labelling errors 12 1.85
No. of cases of wrong sample- reporting slip match 7 1.1 No. of samples haemolysed 12 1.85 No. of suspected wrong draws 81 12 No. of actual wrong draws as confirmed on lab analysis 23 3.6 Total no. of samples over this six week period 675 TRANSPORTATION ERRORS 01-Jul 02- Jul 04- Jul 05- Jul 06- Jul 07- Jul 08- Jul 09- Jul 11- Jul 12- Jul 13- Jul 14- Jul 15- Jul 16- Jul 18- Jul No. of haemolys ed samples received at the lab 2 1 2 3 2 2 10 2 1 1 1 1 No. of samples haemolys ed at the collection centre itself 1 1 3 No. of samples haemolys ed during transport ation 1 1 1 3 2 2 7 2 1 1 1 1 Total no. of samples transport 93 90 123 101 109 97 102 91 154 113 90 100 107 96 123
ed during the day % of samples haemolys ed during transport ation 1.07 1.1 0.83 3.3 2.1 2.1 4.5 1.78 1.11 1 0.94 0.83 19 Jul 20 Jul 21 Jul 22 Jul 23 Jul 25 Jul 26 Jul 27 Jul 28 Jul 29 Jul 30 Jul 1Aug 2Aug No. of hemolyse d samples received at the lab 3 1 1 2 3 1 1 1 1 1 No. of samples hemolyse d at the collection centre itself 1 1 2 1 No. of samples hemolyse d during transport ation 2 1 1 1 1 1 1 1 1 Total no. of samples transport ed during the day 108 110 111 102 75 132 100 96 104 100 87 129 116 % of samples hemolyse d during transport ation 1.9 0.91 0.9 0.99 0.77 1 1.15 0.76 0.86 No. of hemolyse d samples received at the lab 3 1 1 2 3 1 1 1 1 1 03- Aug 04- Aug 05- Aug 06- Aug 08- Aug 09- Aug 10- Aug 11- Aug 12- Aug 13- Aug 16- Aug
No. of hemolysed samples received at the lab 3 3 2 2 2 No. of samples hemolysed at the collection centre itself 1 2 No. of samples hemolysed during transportation 2 2 Total no. of samples transported during the day 111 115 95 82 130 104 69 118 104 59 108 % of samples hemolysed during transportation 2.49 1.89 This table seeks to identify and quantify the magnitude of TRANSPORTATION ERRORS Samples are transported in a sealed box, but due to excess patient load and shortage of boxes, sometimes the lid remains open, which is a possible source of error. About 100 samples are transported in one box, specimens are transported from the phlebotomy centre to the lab at 12:30 p.m., the whole day's quota together.% haemolysis of samples is a good measure of transportation errors . Samples received at the lab: 01- Jul 02- Jul 04- Jul 05- Jul 06- Jul 07- Jul 08- Jul 09- Jul 11- Jul 12- Jul 13- Jul 14- Jul Total no. of samples for the day 93 90 123 101 109 97 102 91 154 113 90 100 No. of samples hemolyzed 2 1 2 3 2 2 10 2 1 1 % of samples hemolyzed 2.16 1.11 1.65 3.3 2.06 1.98 6.5 1.78 1.1 1 No. of samples chylased 1 % of samples chylased 1.76 No. of Qty. 1
insufficient cases No. of wrong entries- identification errors 3 1 2 No. of Double entries 1 Total error % 3.92 1.11 1.65 3.3 0.92 5.14 1.98 0 7.35 4.42 1.1 1 15- Jul 16- Jul 18- Jul 19- Jul 20- Jul 21- Jul 22- Jul 23- Jul 25- Jul 26- Jul 27- Jul 28- Jul 29- Jul Total no. of samples for the day 107 96 123 108 110 111 102 75 132 100 96 104 100 No. of samples hemolyzed 1 1 3 1 1 2 3 1 1 % of samples hemolyzed 0.94 0.9 2.78 0.9 0.9 1.96 2.25 1 0.96 No. of samples chylased 1 1 % of samples chylased 0.9 1.96 No. of Qty. insufficient cases No. of wrong entries- identification errors 1 1 No. of Double entries Total error % 1.89 0 0.9 2.78 1.8 1.8 3.92 0 2.25 1 0 0.96 0 Haemolysis is one of the commonest pre analytical errors in the pre-analytical stage.On some days,such as on 11 jul,when as many as 10 such samples were received,the % error came out to be as much as 7.35%,though on an average,it isn't more than 2.5%. Patient misidentification errors,though forming a small fraction,become significant on days when there is huge sample load. Data entry errors such as Double entry ,though rare are entirely human fault and need to be avoided.
On one odd occasion,there was a case where sample was Quantity insufficient. Chylous samples too aren't useful to a lab diagnostician and have to be discarded. NOTE-All % more than 5% have been indicated in red to denote gross disparity. 01- Aug 02- Aug 03- Aug 04- Aug 05- Aug 06- Aug 08- Aug 09- Aug 10- Aug 11- Aug 12- Aug 13- Aug 16- Aug No. of samples hemolyzed 1 1 3 3 2 2 2 % of samples hemolyzed 0.8 0.86 3.67 2.85 1.72 1.86 No. of samples chylased 2 % of samples chylased 1.54 No. of Qty. insufficient cases No. of wrong entries- identification errors 1 1 1 No. of Double entries 1 Blood-urine sample exchange 1 1 Miscellaneous errors 1 Sample not received 1 Total no. of samples in the day 129 116 111 115 95 82 130 104 69 118 104 59 108 Total % of error 0.86 1.72 0 0.85 1.53 3.67 1.54 3.85 0 2.54 0.96 6.67 1.86 No. of errors % No. of sample collecti on 23 3.6
23 0.034074074 0.0203877 0.0477604 57 0.084444444 0.063468 0.1054209 13 0.019259259 0.0088911 0.0296274 39 0.057777778 0.0401758 0.0753797 Calculation of Confidence Intervals 95% CI FOR PROPORTION 95% C.I. lower limit upper limit 3.41 2.04 4.78 8.44 6.35 10.54 1.93 0.89 2.96 5.78 4.02 7.54 It was found that in 3.6% cases, there were sample collection errors with 95% C.I. 2.04% to 4.78%. It was found that in 8.4% cases, there were improper samples received with 95% C.I. 6.35% to 10.54%. It was found that in 1.8% cases, there were patient identification errors with 95% C.I. 0.89% to 2.96% It was found that in 5.4% cases, there were transportation errors with 95% C.I. 4.02% to 7.54% errors No. of improp er sample s receive d, 57 8.4 No. of patient identifi cation errors 13 1.8 No. of transpo rtation errors 39 5.4 Total sample size 675
DISCUSSION: The number of old and obese patients who come for phlebotomy form a major chunk of errors occurring in the collection centre. Venous localization in such patients is often difficult, hence leading to wrong pricks, haemolysis, chylasing and chances for patient infection as well as needle stick injuries to the phlebotomist. Tying the tourniquet too tight/for too long increases chances of haemolysis. Syringe draws, used especially for small children and when normal draws are too difficult, form a major chunk of collection errors. Excessive application of pressure in drawing blood might cause haemolysis, thus vacuum draws through a vacutainer are preferred. Double and triple pricks not only adds to patient discomfort, but also leads to increasing patient susceptibility to infection, anaphylactic shock etc.Labelling errors, sample exchange, wrong sample-reporting slip match, quantity insufficient, collections done in wrong tubes, patient identification errors form a substantial chunk of purely mechanical errors that can easily be eliminated. Errors during transportation are most difficult to identify and rectify because it is difficult to determine the cause of variations and hence, whether it actually qualifies as an error or a variable. On some days, the % of transportation errors might go up to as much as 4.5% as stated in the table. Some specimens such as Arterial Blood Gases need to be transported immediately and others such as specimens for serum or plasma chemistry testing need to centrifuged and stored within 2 hrs. after collection. Though the centrifugation part is taken care of, the time lag between collection and transport proves expensive. Pre analytical variables such as age,gender,pregnancy,nutritional status,diet,exercise,obesity,lifestyle,etc. may alter test results significantly and are all the more difficult to detect. Variables are far more difficult to eliminate, especially the uncontrollable ones. However, some such as dietary habits; posture, physical training etc. can be controlled. Several discrepancies between expected and actual outcomes can be attributed to these variables. Knowledge of such variables and errors will reduce the margin of anomalies and the scope for wrong reporting shall go down drastically. CONCLUSIONS: This study suggests that preanalytical errors and variables do play a significant role in abnormal/non concomitant test reports. As in this setup, improper draws especially in old, obese patients and children <5 years form the major chunk of collection errors. Transportation errors form a big fraction of the total preanalytical errors. Upon arrival in the lab, haemolysed samples are the biggest hindrance to correct reporting and have to be discarded immediately. Sample storage does not present a significant challenge to reporting in this setup as within half an hour from the time of arrival, all samples are centrifuged and appropriately stored. These errors are cumulative and if stringent practices are followed right from sample collection, the chances of errors in later stages are subsequently reduced, thus preventing discomfort/infection to the patient, besides saving time and money on recollections and resulting in accurate reporting, thereby leading to apt diagnosis and correct treatment.
SUMMARY: There are several discrepancies between expected lab reports and the actual ones, which we tend to blame on faulty equipment and analytical errors. These can be attributed to preanalytical variables and errors. How significantly these affect test results is what this project seeks to understand through a 6 week long prospective study followed by 2 weeks of analysis. The methodology used involves a questionnaire, interaction with doctors, phlebotomists and patients concerned; observations at the phlebotomy centre, Civil OPD, Southern Command Hospital, Dept. Of Biochemistry, AFMC; ICU (Med. and Surg.).As evident in the report, a major chunk of preanalytical errors in the collection centre can be attributed to difficult venous localisation and improper venipuncture, especially in old, emaciated individuals, small children and obese persons. Syringe draws and application of excess pressure are often the culprits behind haemolysis. Besides, collections of sample in wrong tubes (with wrong anticoagulant), inadequate draws and sample mix-ups on busy days add on to the problem. Transportation errors are a major grey area as nothing much is done to protect against vagaries of photo radiation, temperature changes, moisture etc. The root cause stems from the inability to identify the source of the error and the enormous expenditure in procuring boxes that will nullify such variables, rendering it impracticable in routine practice. A good number of haemolysis of samples occurs in transit.Chylased and lipemic samples, wrong entries in registers, exchange of blood-urine sample though contributing an insignificant percentage, are totally mechanical errors that can easily be got rid of. Variables such as diet, exercise, obesity, lifestyle, gender, age etc. are far more difficult to eliminate in a setup such as this and much more needs to be done to account for these. Sound knowledge of these preanalytical errors and variables shall play an important role in differentiating genuine wrong reporting from discrepancy in expected and actual test results arising because of such factors.
SUGGESTIONS: This project should be repeated at various clinical and laboratory settings all over the country with a much larger sample size and a longer study period and findings should be correlated to account for local factors. Meanwhile, better equipment should be procured and will surely result in a decrease in faulty reporting and improve reliability of test results. REFERENCES: 1. Pierangelo Bonini, Mario Plebani, Ferruccio Ceriotti, et al.Errors in Laboratory Medicine. Clinical Biochemistry, 2002; 48:691-698. 2.Dzik WH,Murphy MF,Andreau G,et al.An international study of the performance of sample collection from patients.Vox Sang 2003;85:40-7. 3. Lumadue JA, Boyd JS, Ness PM.Adherence to a strict specimen-labeling policy decreases the incidence of erroneous blood grouping of blood bank specimens. Transfusion 1997; 37:1169-72. 4. A.S.Kanagasabhapathy.Effective laboratory quality management towards preventing medical liability cases.IJCB 25(1):1-3, 2010. 5.14. Wallin O,So”derberg J, Van Guelpen B, et al.patient-centred care-preanalytical factors demand attention: a questionnaire study of venous blood sampling and specimen handling. Scand J Lab Invest 2007; 67:836-47
Preanalytical variables and errors in sampling
Preanalytical variables and errors in sampling