Preanalytical error clinical chemical tests

Preanalytical error clinical chemical tests

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  Preanalytical Errors in MedicalLaboratory Meeqat General Hospital, 25 October 2016 By Prof. Asmaa El Reweny, MD Professor & Consultant of Clinical & Chemical Pathology, Faculty of Medicine, Cairo University & AMS, Taibah University (2006-2016)
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  Objectives At the endof this lecture you will be able to: 1- Identify what is meant by preanalytical period. 2- Recognize magnitude of preanalytical errors in relation to total analytical errors. 3- Identify steps of preanalytical process & its potential errors. 4- Recognize how to avoid these errors 5- Identify markers for sample rejection 2Prof Asmaa El Reweny, MD
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  Introduction  Three phasesof laboratory testing:  Pre-analytical: Specimen collection, transport & processing  Analytical: Testing  Post-analytical: Results transmission, interpretation, follow- up, retesting. 3Prof Asmaa El Reweny, MD
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  Why Preanalytics?  Preanalyticalvariables can dramatically affect the results of laboratory tests.  Paying close attention to control the preanalytical variables will help to ensure accurate test results in clinical laboratory.
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  Implications of Errors Compromise diagnosis & treatment of the patient • May influence the quality of final results ... • Errors made in the period prior to the analysis ... No result is better than bad result. Accurate result is the best of all. 5Prof Asmaa El Reweny, MD
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  Steps of preanalyticalphase Preparation prior to sampling Sampling/handling Transport/Storage Preparation prior to analysis 6Prof Asmaa El Reweny, MD
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  “The weak link” Thepreanalytical phase is the weak link in the Patient Focus Circle. The more steps involved in a process, the more likely there will be errors.
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  Magnitude of PreanalyticalErrors In Relation To Total Analytical Errors  93% (2014)  32 - 75% * *Stankovic 2008 “Quality Improvements in the Preanalytical Phase: Focus on Urine Specimen Workflow” 8Prof Asmaa El Reweny, MD
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  9 Sources of LabErrors
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  Error Source Ross and Boone1Plebani et al.2 Pre-analytical 46% 68% Analytical 7% 13% Post-analytical 47% 19% 1 – Ross and Boone, Inst. of Critical Issues in Health Lab Practices, DuPont Press, 1991 2 - Plebani and Carraro. Clin Chem 43:1348, 1997 Total Analytical Error Distribution
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  Pre-analytical errors  Pre-&post-analytical errors: > 90% of errors  These potential errors are not inevitable but could be prevented with a diligent application of quality control, continuing education and effective collection systems. 11Prof Asmaa El Reweny, MD
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  Steps of Pre-Analyticalprocess  Patient Identification  Sampling Technique Outside Lab  Collection Procedures  Specimen Transport  Specimen Processing Inside Lab 12Prof Asmaa El Reweny, MD
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   Attention tothe preanalytical variables associated with blood collection is critical in ensuring accurate test results.  Record significant variables on request form. Effects of Pre-analytical Variables on Quality of Laboratory Testing 14Prof Asmaa El Reweny, MD
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  Effects of Pre-analyticalVariables on the Results of Laboratory Testing  Some patient variables that affect test results - Age - Genetic variation/ Race - Sex - Nutritional status - Diet - Diagnostic & therapeutic - Drugs procedures (PR, endoscopy) - Exercise - Pregnancy - Posture - Timing: Biorythm - Special habits - Hemolysis, lipemia, Jaundic - Diagnosis (provisional) 15Prof Asmaa El Reweny, MD
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  Change (%) ofserum concentration of different analytes after a standard meal
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  When identifying thepatient, get:  Full name  Age & sex  Address/Nationality  Identification number: Hospital No for inpatients, Identification band should contain the above information (confirm before venipuncture). Patient and specimen identification 17Prof Asmaa El Reweny, MD
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   Patient Identification:It is important to identify a patient accurately so that blood is collected & labeled from the correct person with his correct data. (otherwise mislabeling ???) 18Prof Asmaa El Reweny, MD
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  Patient and specimenidentification  The highest frequency of errors occurs with the use of handwritten labels & request forms.  These can be eliminated by:  Confirming patient’s identifiers (name, medical record number, date of birth, room location or address)  Barcode technology.
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   Locate Patient Prepare Patient  Draw Sample  Label  Dispose of supplies Sampling and Collection 20Prof Asmaa El Reweny, MD
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  Sample Collection  Timingof Collection  Therapeutic Drug Monitoring  Peak and trough collection times  Basal State Collections  Fasting requirements: no food or liquid except water (10-12h), (12-14 h for TG)  2h postprandial, from the start of food .  Specimens affected by time of day, for example, cortisol, iron and TSH. 21Prof Asmaa El Reweny, MD
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  Diurnal variation ofselected analytes Analytes (serum, urine) Maximum (time of day) Minimum (time of day) Amplitude % of daily mean Cortisol (S,U) 5-8 21-3 180-200 Prolactin 5-7 10-12 80-100 Aldosterone 2-4 12-14 60-80 Renin 0-6 10-12 120-140 Iron (S) 14-18 2-4 50-70 Phosphate (S) 2-4 8-12 30-40 Phosphate (U) 18-24 4-8 60-80
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  Timing of Collection Between 7 and 9 a.m.  Before interfering diagnostic and therapeutic procedures  In drug monitoring: consideration of the peak after administration and the steady state phase before the next dose  Documentation of the exact time of sampling is very important !
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  Phlebotomy  Venipuncture requiresexpert knowledge and critical judgment.  Phlebotomy errors may cause harm to patients or result in needle stick injury to the phlebotomist.  It could result in many preanalytical errors in Lab results. 24Prof Asmaa El Reweny, MD
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  Error Prevention  PhlebotomyEducation  Academic course and training under the supervision of a senior phlebotomist.  Continuous Medical Education  Competency assessments (written and observational).  Professional Licensure.  Phlebotomy Staffing  Adequate staffing to maintain collection standards.  Technology  Use of barcode scanners for patient identification. 25Prof Asmaa El Reweny, MD
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  Phlebotomy Technique 1. Posture: -Comfortably seated patient or supine for 20 min before sampling (not standing). - The arm should be extended in a straight line from the shoulder to the wrist. 2. Collection site. - The median cubital vein is the preferred site. - Veins on the hand or at ankle may be used. 26Prof Asmaa El Reweny, MD
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  Increase (%) ofplasma concentration of various analytes when changing from supine to an upright position
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  Phlebotomy Technique  Cleaningof venipuncture site  Thorough cleaning with alcohol  Allow alcohol to dry completely to avoid stinging sensation and hemolysis of sample  Iodine for blood culture samples (sterile sample) NB: contamination occurs in 50% at some hospitals with increased costs & patient overtreatment. 28Prof Asmaa El Reweny, MD
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  Collection site Avoid thearm with: - Extensive scarring, hematoma, infection, edema or burn - On the same side of mastectomy. - I.V. infusion (Document if IV ). 29Prof Asmaa El Reweny, MD
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  Phlebotomy Technique 3. Correctcollection system  Vacutainers for large veins in antecubital fossa.  Syringe for small, fragile veins or veins outside antecubital fossa. 4. Venous access  Needle entry should be at 15-30o depending on depth of vein.  Needle entry should be in same direction as vein, centered over vein.  Anchor vein to prevent movement during needle entry and to reduce pain to patient. 30Prof Asmaa El Reweny, MD
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  31Prof Asmaa ElReweny, MD
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  Phlebotomy Technique Errors Tourniquet Application  Tourniquet tied too close to venipuncture site can cause hematoma.  Veins may not become prominent if tourniquet is tied too high (> 3-4 inches above venipuncture site)  Tourniquet left for > 1 min can result in hemoconcentration, affecting some test results.  Tourniquet should be released as soon as needle is in the lumen of vein and blood flow is established. 32Prof Asmaa El Reweny, MD
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  Change (%) inserum concentration of various analytes after tourniquet application time of 6 min
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  Collection  Additives used: -EDTA, - Citrate, - Lithium heparin, - Fluoride/ Oxalate 34Prof Asmaa El Reweny, MD
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  Selection of tubes- Common problems Solution: New sample needs to be sent to lab. Typical errors Consequences Incorrect tube • cannot be analysed • risk of contamination Incorrect order of tubes • contaminations • false results
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  Common problem: Hemolysis Causes of Hemolysis  Traumatic venipuncture  Blood collected from area with hematoma  Vigorous shaking after collection  Milking the site when collecting capillary samples  Blood collected using a small diameter needle.  High filling pressure through a narrow entrance (e.g during too vigorous sample aspiration)  Cooling down the sample < 0 °C. 36Prof Asmaa El Reweny, MD
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  Hemolysis: Affects analytes thatare present at higher concentrations in erythrocytes than in plasma (K, LD, AST, Mg, P, ACP) Hemolysis may also affect unblanked analytical methods. 37Prof Asmaa El Reweny, MD
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  Collection  Capillary Collections: Appropriate site  Heel stick: sides of bottom surface of the heel (infants)  Finger stick: third or fourth fingers, perpendicular to fingerprint lines on fleshy pads on finger surface.  Warm before collection to increase capillary blood flow near skin surface.  Clean site with alcohol and allow to dry.  Discard first drop of blood. 38Prof Asmaa El Reweny, MD
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  Recommended order ofdraw (NCCLS): 1. Blood Culture Bottles 2. Coagulation Tube 3. Serum Tube with or without clot activator, with or without gel separator 4. Heparin Tube with or without gel plasma separator 5. EDTA 6. Glycolytic Inhibitor 39Prof Asmaa El Reweny, MD
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  Correct Specimen Volume (bloodto additive ratio).  Little blood in heparin tube makes heparin relatively higher in concentration and may potentially interfere with some chemistry analysis  In Coagulation Studies incomplete filling results in specimen dilution and prolonged Prothrombin Time & PTT results. 40Prof Asmaa El Reweny, MD
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   Proper TubeMixing: All tubes with additives need to be inverted (10 times) to mix the additive evenly with the blood. Improper mixing of the tube after venipuncture could contribute to sample clotting. 41Prof Asmaa El Reweny, MD
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  Sampling - Commonproblems Typical errors Consequences Trauma, strangulation, stasis hemolysis, hemoconcentration IV contamination dilution, false results Sample volume is insufficient incomplete lab results, repeat sampling Incomplete filling of tubes inappropriate anticoagulant:blood ratio, false results Inappropriate mixing clotted, hemolysed sample Solution: Lab report with preanalytical comment (if problem recognized). New sample is requested.
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  Infusions/transfusions as interferingfactor and/or contaminants of laboratory tests Infusion/ transfusion Analyte affected Trend Comments Electrolytes K, Na, Mg  contamination Glucose glucose  contamination inorg. phosphate, K  insulin amylase, bilirubin  up to 15%, particularly in neonates Dextran Thrombin time  5-10 sec slower total protein  Method- dependent urea 
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  Infusion, transfusion, catheters Blood should never be collected proximal to the infusion site.  It is recommended that the laboratory be informed of when and what type of infusion were carried out and when blood samples were taken.  If samples are to be taken from catheters, the cannula should be rinsed with isotonic saline suitable for the volume of catheter. The first 5 ml of blood should be discarded before a blood sample is taken.
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  Some points insampling from A-lines Preparation prior to sampling Sampling/ handling •Label with patient ID. •Use dry electrolyte balanced heparin. •Keep patient respiratory condition stable for a certain period prior to sampling. •Make sure that the A-line has been adequately cleared of flush solution. •Aspirate the sample slowly to prevent degassing & hemolysis. •Expel any air bubbles immediately after sampling. •Mix sample thoroughly with heparin after sampling. 45Prof Asmaa El Reweny, MD
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  Sufficient mixing withheparin  Insufficient mixing can cause coagulation of the sample  Invert the syringe 10 times and roll it between your palms 46Prof Asmaa El Reweny, MD
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  Transportation to theLaboratory
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  Specimen Transport - Time -Temperature - Light 48Prof Asmaa El Reweny, MD
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  Blood Specimen Transport Proper transport of specimens after collection ensures quality of sample (& tests).  Timing  Some specimens must be transported immediately (Arterial Blood Gases).  Specimens for serum or plasma chemistry testing should be centrifuged and separated within 2 hs. 49Prof Asmaa El Reweny, MD
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  Transport Errors  Temperature Onice: ABGs, Ammonia Warmed (37 C): cryoglobulins Avoid temperature extremes if transported via vehicle.  Transport Container  Some samples need to be protected from light e.g. bilirubin.  Transport in leak-proof plastic bags in lockable rigid containers & avoid agitation. 50Prof Asmaa El Reweny, MD
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  Transportation - Commonproblems Typical errors Consequences Delay False results (high K) Delay in reporting Burden and harm to patient sample stability deteriorates, certain components break down Inappropriate storage Solution: New sample is requested.
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  Special Handling ofBlood Specimens:  Chilled tube: To maintain stability of some analytes, a slurry of ice & water is recommended for chilling. Examples : 1. ACTH, PTH, Catecholamine & Renin 2. Angiotensin Converting Enzyme (ACE), 3. Acetone, Ammonia,, Free Fatty Acids, Lactic Acid, Pyruvate… 52Prof Asmaa El Reweny, MD
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  Intra-laboratory Handling, Preparation andStorage of Samples  Registration, identification  Checking for clots  Centrifugation  Distribution  Storage (non routine daily analysis , for post-analysis if it is needed)
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  Intra-laboratory handling – Commonproblems Typical errors Consequences Native blood centrifugated before clotting Hemolysed sample, fibrin strand in serum, clogging Inappropriate melting of frozen specimens False concentration or precipitation, …… false result Inappropriate storage of samples in lab (sample ID lost, contamination, break down of unstable components … etc.) False results Contamination Clots in anticoagulated blood Cryoglobulins False results Solution: New sample is requested when necessary.
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  Common Interferences Typical errorsConsequences in vitro hemolysis •High K, LDH, HB •interference with many analytical procedures Hyperlipidaemia •Pseudo-hyponatraemia •Interference with many analytical procedures Hyperbilirubinaemia •Interferences Drugs •Interference Solution: - New sample is requested. - Alternative methods used. - Results commented.
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  Changes in variousanalytes with increasing hemolysis
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  Quality Markers for Rejectionof Samples  Clotted  Hemolyzed  Underfilled, overfilled  Insufficient quantity  Incorrect labeling  Unlabeled specimen  Incorrect patient  Incorrect specimen  Contaminated  Lost sample  Too old to process  Broken and leaking 57Prof Asmaa El Reweny, MD
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  Finally…  The humanrole in sample collection makes complete elimination of errors associated with laboratory testing unrealistic  However, good practices and compliance with strategies for error prevention can lead to a substantial reduction in pre-analytical errors. Thank You 58Prof Asmaa El Reweny, MD
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  References [ 1] Magee,L. S. Preanalytical variables in the chemistry laboratory. Becton Dickinson Lab Notes 2005; 1 (1) [2] Sarstedt AG: Tipps und Tricks in der Preanalytik, 2008 [3] Tyndall, L. Managing Preanalytical Variability in Hematology. Becton Dickinson Lab Notes 2004; 14 (1) [4] WHO guidelines on drawing blood: best practices in phlebotomy, 2010 Prof Asmaa Elreweny, MD59
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  ‫العالمين‬‫رب‬ ‫هلل‬ ‫الحمد‬ ‫التنزيل‬‫مواطن‬ ‫شهدت‬ ‫بلدة‬ ‫هي‬ ‫وجبرائيل‬ ‫ميكائيل‬ ‫اتها‬‫طرق‬ ‫في‬ ‫مشى‬ 60 Prof Dr Asmaa El-Reweny