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  1. Pre-analytical Laboratory Errors Dr Sami Saeed Associate Professor/HOD Foundation University Medical College Path Lab, Fauji Foundation Hospital, Rawalpindi Email:
  2. Objectives  Identify the significant pre-analytical errors that can occur during blood specimen collection and transport  Explain the various means of pre-analytical error prevention  List proactive steps to reduce potential pre- analytical errors associated with blood collection and transport
  3. Introduction  Three phases of laboratory testing: pre-analytical, analytical and post-analytical  Pre-analytical—specimen collection, transport and processing  Analytical—testing  Post-analytical—results transmission
  4. Pre Analytical Phase  Specimen collection, handling and processing  Physiological variables such as the effect of lifestyle, age, gender, pregnancy and menstruation  Endogenous variables such as drugs etc
  5. Pre Analytical Phase  Some such as specimen variables can be controlled  Knowledge of uncontrollable variables need to be well understood
  6. Pre Analytical Phase  German Society for Clinical Chemistry and the German Society for Laboratory Medicine proposed comprehensive recommendations on the quality of diagnostic samples, handling of hemolytic, icteric and lipemic samples  Choice of anticoagulants to use, optimal sample size and analyte stability in sample matrix for each analyte
  7. Recommendations of the German Society for Clinical Chemistry and the German Society for Laboratory Medicine  Optimal sample volume: Twice the analytical volume of serum or plasma required for laboratory tests plus the dead volume of sample cup, replicates, and secondary tubes  In general, for testing 20 analytes in clinical chemistry, 3 to 4 mL of whole blood is needed to obtain heparinized plasma, while 4 to 5 mL of clotted blood is needed to express serum  2 to 3 mL of EDTA blood and citrated blood is sufficient to perform hematology and coagulation tests
  8. Pre-analytical errors  Pre (32-75%)- and post-analytical errors are estimated to constitute 90% of errors
  9. Clinical Chemistry 53:7 1338–1342 2007 Errors in the Total Test Process Pre-analytical Analytical Post-analytical 62% 23% 15%
  10. Types of Errors  Patient Identification  Phlebotomy Technique  Test Collection Procedures  Specimen Transport  Specimen Processing
  11. Patient Identification Errors  Errors in correctly identifying the patient are indefensible  Reasons for patient identification errors  Proper positive patient identification procedures not followed  Identification bracelet (inpatients)  Asking patients to state their full name (inpatients/outpatients)  Patient identification by staff or family member if patient unable to identify him/herself
  12. Patient Identification Errors  Collection tubes labeled with the wrong patient  Collection tubes not labeled at the time of collection  Wrong labels affixed to collection tubes at bedside  Collection tubes incorrectly labeled by someone other than the phlebotomist who collects the specimen
  13. Patient Complications  Some patient variables that affect blood specimens  Diet  Fasting  Exercise  Obesity  Allergies to alcohol or iodine used to clean venipuncture site  Use alternative cleanser such as chlorhexidine
  14. Patient Identification Errors Specimen tubes unlabeled Requisition or collection tube labels not affixed to tubes  Requisition or collection tube labels in bag containing collection tubes  Requisition or collection tube labels rubber- banded to tubes  Collection tube labels not affixed to all tubes  Specimen collection tubes labeled insufficiently
  15. Phlebotomy Errors  Phlebotomy is a highly complex skill requiring expert knowledge, dexterity and critical judgment  It is estimated that one billion venipunctures are performed annually in the U.S  Phlebotomy errors may cause harm to patients or result in needlestick injury to the phlebotomist
  16. Phlebotomy Technique Errors  Phlebotomy technique is important  Ensures test result validity  Minimizes trauma to patient  Minimizes potential for phlebotomist injury  Reduces recollections  Vein selection essential for successful venipuncture  Three veins in antecubital fossa in order of selection (1) median cubital (2) cephalic (3) basilic
  17. Phlebotomy Technique Errors  Venous Access Difficulties  Obstructed, hardened, scarred veins  Veins difficult to locate  Use of Alternative sites  Top of hand/Side of wrist  Vein Collapse  Use of appropriate needle size  Smaller evacuated collection tube
  18. Phlebotomy Technique Errors  Site Selection  Avoid sites with IV  Use alternative arm or draw below IV to avoid contamination/dilution from IV  Document arm if IV  Mastectomy—avoid site due to lymphostasis  Infection risk/alteration in body fluids and blood analytes  Edematous areas —avoid due to accumulation of body fluids  Possible contamination/dilution of specimen
  19. Phlebotomy Technique Errors  Tourniquet Application  Tourniquet tied too close to the venipuncture site can cause hematoma  Veins may not become prominent if tourniquet is tied too high (more than 3 to 4 inches above venipuncture site)  Tourniquet left on longer than one minute can result in hemoconcentration, affecting some test results  Tourniquet should be released as soon as needle is in the lumen of the vein and blood flow established
  20. Phlebotomy Technique Errors  Cleansing of venipuncture site  Thorough cleaning with alcohol  Allow alcohol to dry completely to avoid stinging sensation upon needle entry and hemolysis of sample  Samples such as blood cultures should be collected using iodine to cleanse site to ensure sterility of sample  Recollection rate for blood cultures ranges due to contamination is as high as 50% in hospitals with increased costs, patient overtreatment
  21. Test Collection Errors  Order of Draw  Order of draw affects the quality of the sample and can lead to erroneous test results due to contamination with the additive from the previous blood collection tube  Hemolysis  Blood collected insufficient to amount of additive in tube,  Traumatic venipuncture  Blood collected from area with hematoma  Vigorous shaking of tubes after collection  Milking the site when collecting capillary samples and blood collected using a small diameter needle.
  22. Order of Specimen Collection  Blood culture tube  Coagulation tube (citrate)  Serum tube (with or without clot activator or gel separator)  Heparin (with or without gel separator)  EDTA  Oxalate/ Fluoride  NCCLS (CLSI) H3-A5 standard, 2003
  23. Test Collection Errors  Timing of Collection  Timed Draws  Therapeutic Drug Monitoring  Peak and trough collection times  Basal State Collections  Fasting requirements—no food or liquid except water  Specimens affected by time of day, for example, cortisol
  24. Test Collection Errors  Collection tube not completely filled  Example— Incomplete filling results in specimen dilution and erroneous Prothrombin and aPTT test results
  25. Test Collection Errors  Capillary Collections—finger stick or heel stick  Appropriate site  Heel stick—sides of the bottom surface of the heel  Finger stick—third or fourth fingers, perpendicular to fingerprint lines on fleshy pads on finger surface  Warming—Warm before collection to increase capillary blood flow near skin surface  Cleaning—cleanse site with alcohol and allow to air dry
  26. Capillary Collections  Massaging site to increase blood flow  Milking site can cause hemolysis or tissue fluid contamination  Finger sticks—roll fingers toward fingertip at 1st finger joint several times  Heel sticks—gently squeeze infant’s heel before performing puncture.  Perform puncture while firmly squeezing finger or heel  Wipe away first two drops of blood  Ensure that full blood drop wells up each time
  27. Capillary Collections  Avoid touching capillary collection tube or micro collection tube to skin or scraping skin surface  Contaminates puncture site  Blood may become hemolyzed  Mixing micro collection tubes with additive frequently to avoid micro clots  Collecting tubes with additives first  Protecting tubes for bilirubin from light
  28. Specimen Transport Errors  Timing  Some specimens must be transported immediately after collection, for example Arterial Blood Gases  Specimens for serum or plasma chemistry testing should be centrifuged and separated within two hours
  29. Transport Errors  Temperature  Specimens must be transported at the appropriate temperature for the required test  On ice—ABGs, Ammonia  Warmed --98.6 degrees (37 C), cryoglobulins  Avoid temperature extremes if transported from via vehicle from other collection site  Transport Container  Some samples need to be protected from light, for example, bilirubin  Transport in leak-proof plastic bags in lockable rigid containers
  30. Physiological Pre Analytical Variables  TIME  Increased/Decreased  Cortisol Toward evening and midnight  Glucose tolerance test values Afternoon  SEASON  Increased/Decreased  Summer  Vitamin-D , Triidothyronine 20%  Winter Total cholesterol (slight)Triglycerides  MENSTRUATION  Increased/Decreased  Serum iron and phosphate  Cholesterol, lowest at ovulation  CAFFEINE  Increased/Decreased  cAMP  Free fatty acids  Free ionic calcium  Plasma renin and catecholamine  SMOKING  Increased/Decreased  Plasma Epinephrine  Carboxyhemoglobin, Hemoglobin, RBC, WBC, MCV, HDL-C
  31. Tests Referred 01st Jan 2013-30th June 2013 OPD Wards Chemical Pathology 1,25,932 1,26,887 Hematology 79,840 81,257 Microbiology 32,159 30,541 Total 2,37,931 2,38,685
  32. Total Number of Errors  OPD and Wards: 196405 (41%)
  33. The Errors! Type of error Inpatients Outpatients Hemolyzed sample Clotted sample Incorrect sample No Label or ID Insufficient sample Incomplete Info (blood group) Empty tube Total 67566 53700 33764 16725 7608 5862 7664 192889 828 1015 456 857 208 - 152 3516
  34. Causes, Probable (?)  Improper mixing  Labeling by junior/untrained staff  Sample ordering system operated by Nursing staff  Sample transport to lab by wards boys/ayas  Lack of knowledge about sampling requirements in PGT’s
  35. Review of the literature on laboratory errors Sector of the laboratory Lapworth and Teal Clinical chemistry Goldschmidt and Lent Whole laboratory Nutting et al. Primary care Plebani and Carraro Stat laboratory Stahl et al. Whole laboratory Hofgärtner and Tait Molecular genetic tests onsite survey (2 laboratories) Molecular genetic tests questionnaire (101 sent, 42 respondents) Preana- lytical phase 31.6% 53% 55.6% 68.2% 75% 44% 60% Analytical phase 31.6% 23% 13.3% 13.3% 16% 31% 19% Postana- lytical phase 30.8% 24% 30% 18.5% 9% 12.5% 15% Multiple phases 6 % 12.5% 6%
  36. Types of preanalytical errors at the Laboratory of San Raffaele Hospital, Italy Type of error Inpatients Outpatients Hemolyzed sample Insufficient sample Incorrect sample Clotted sample Incorrect identification Lack of signature (blood group) Empty tube Lack or wrong compilation of the accompanying module Sample not on ice Tube broken in the centrifuge Test not reserved Urine not acidified Open container Module without signature Urine volume not indicated Total 8494 3256 1824 792 287 266 238 120 75 57 31 24 20 14 5 15,503 256 102 289 80 2 8 6 36 13 792
  37. Error Prevention  Phlebotomy Education  Phlebotomists should undergo thorough on-the-job training under the supervision of a senior phlebotomist  Continuing Education  Phlebotomists should participate in regular educational competency assessments (written and observational)  Phlebotomy Staffing  Adequate staffing to maintain collection standards  Technology  Use of barcode scanners for patient identification
  38. Recognition of Pre analytical Variables Causing Changes in Laboratory Results  A 55-year-old man was hospitalized with a serum potassium of 6.9 mmol/L on a non- hemolyzed sample obtained in an outpatient clinic. All other laboratory tests were normal. During hospitalization serum potassium values ranged from 3.9 - 4.5 mmol/L (normal 3.5 - 5.0 mmol/L).
  39. Recognition of Pre analytical Variables Causing Changes in Laboratory Results  In OPD, blood was collected with the application of tourniquet and fist clenching  In the ward, blood was collected through an in- dwelling catheter  Cause of pseudohyperkalemia was repeated fist clenching during tourniquet application intended to make the veins prominent  The contraction of forearm muscles causes release of potassium. This effect can lead to a 1-2 mmol/L increase in potassium with as much as 2.7 mmol/L increase
  40. Recognition of Pre analytical Variables Causing Changes in Laboratory Results  Abnormal laboratory findings in a 43 year old male: Alkaline phosphatase 5 IU/L (normal 45-115 IU/L), calcium 0.5 mmol/L (normal 2.1 - 2.6 mmol/L) and potassium 22.0 mmol/L (normal 3.5-5.0 mmol/L) on a non-hemolyzed sample.
  41. Recognition of Pre analytical Variables Causing Changes in Laboratory Results  Plasma was obtained from blood collected in a tri potassium EDTA tube  EDTA chelated magnesium and zinc required for the activity of alkaline phosphatase; EDTA also chelated calcium leading to its gross underestimation  Potassium in EDTA was responsible for raised K+to a physiologically impossible level.
  42. Discussion  How are pre-analytical errors prevented in your laboratory?  What do you do to prevent human error?  What systems does your hospital use to prevent errors by non-laboratory staff collecting blood?  What pro-active improvements would reduce the number of pre-analytical errors?
  43. Questions?