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Pre-analytical Pre-analytical Laboratory Errors Laboratory Errors
Dr Sami SaeedDr Sami SaeedAssociate Professor/HODAssociate Professor/HOD
Foundation University Medical Foundation University Medical CollegeCollege
Path Lab, Fauji Foundation Path Lab, Fauji Foundation Hospital, Hospital,
Rawalpindi Rawalpindi Email: Email:
[email protected]@comsats.net.pk
ObjectivesObjectives
Identify the significant pre-analytical Identify the significant pre-analytical errors that can occur during blood errors that can occur during blood specimen collection and transportspecimen collection and transport
Explain the various means of pre-Explain the various means of pre-analytical error preventionanalytical error prevention
List proactive steps to reduce List proactive steps to reduce potential pre-analytical errors potential pre-analytical errors associated with blood collection and associated with blood collection and transporttransport
IntroductionIntroduction
Three phases of laboratory testing: Three phases of laboratory testing: pre-analytical, analytical and pre-analytical, analytical and post-analyticalpost-analytical
Pre-analytical—specimen collection, Pre-analytical—specimen collection, transport and processingtransport and processing
Analytical—testingAnalytical—testing Post-analytical—results transmissionPost-analytical—results transmission
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
Pre Analytical Phase
Some such as specimen variables can be controlled
Knowledge of uncontrollable variables need to be well understood
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
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
Pre-analytical errorsPre-analytical errors
Pre (32-75%)- and post-analytical Pre (32-75%)- and post-analytical errors are estimated to constitute errors are estimated to constitute 90% of errors90% of errors
Clinical Chemistry 53:7 1338–1342 2007
Errors in the Total Test Process
Pre-analyticalAnalyticalPost-analytical
62%23%
15%
Types of ErrorsTypes of Errors Patient IdentificationPatient Identification
Phlebotomy TechniquePhlebotomy Technique
Test Collection ProceduresTest Collection Procedures
Specimen TransportSpecimen Transport
Specimen ProcessingSpecimen Processing
Patient Identification Patient Identification ErrorsErrors
Errors in correctly identifying the Errors in correctly identifying the patient are indefensiblepatient are indefensible
Reasons for patient identification Reasons for patient identification errorserrors Proper positive patient identification Proper positive patient identification
procedures not followedprocedures not followed Identification bracelet (inpatients)Identification bracelet (inpatients) Asking patients to state their full name Asking patients to state their full name
(inpatients/outpatients)(inpatients/outpatients) Patient identification by staff or family Patient identification by staff or family
member if patient unable to identify member if patient unable to identify him/herselfhim/herself
Patient Identification Patient Identification ErrorsErrors
Collection tubes labeled with the Collection tubes labeled with the wrong patientwrong patient
Collection tubes not labeled at the Collection tubes not labeled at the time of collectiontime of collection
Wrong labels affixed to collection Wrong labels affixed to collection tubes at bedsidetubes at bedside
Collection tubes incorrectly labeled Collection tubes incorrectly labeled by someone other than the by someone other than the phlebotomist who collects the phlebotomist who collects the specimenspecimen
Patient Complications Patient Complications
Some patient variables that affect Some patient variables that affect blood specimensblood specimens DietDiet
FastingFasting
ExerciseExercise ObesityObesity Allergies to alcohol or iodine used to Allergies to alcohol or iodine used to
clean venipuncture siteclean venipuncture site Use alternative cleanser such as Use alternative cleanser such as
chlorhexidinechlorhexidine
Patient Identification Patient Identification ErrorsErrors
Specimen tubes unlabeledSpecimen tubes unlabeledRequisition or collection tube Requisition or collection tube labels not affixed to tubeslabels not affixed to tubes
Requisition or collection tube labels Requisition or collection tube labels in bag containing collection tubesin bag containing collection tubes
Requisition or collection tube labels Requisition or collection tube labels rubber-banded to tubesrubber-banded to tubes
Collection tube labels not affixed to Collection tube labels not affixed to all tubesall tubes
Specimen collection tubes labeled Specimen collection tubes labeled insufficientlyinsufficiently
Phlebotomy ErrorsPhlebotomy Errors
Phlebotomy is a highly complex skill Phlebotomy is a highly complex skill requiring expert knowledge, requiring expert knowledge, dexterity and critical judgmentdexterity and critical judgment
It is estimated that one billion It is estimated that one billion venipunctures are performed venipunctures are performed annually in the U.Sannually in the U.S
Phlebotomy errors may cause harm Phlebotomy errors may cause harm to patients or result in needlestick to patients or result in needlestick injury to the phlebotomistinjury to the phlebotomist
Phlebotomy Technique Phlebotomy Technique ErrorsErrors
Phlebotomy technique is importantPhlebotomy technique is important Ensures test result validityEnsures test result validity Minimizes trauma to patientMinimizes trauma to patient Minimizes potential for phlebotomist injuryMinimizes potential for phlebotomist injury Reduces recollectionsReduces recollections
Vein selection essential for successful Vein selection essential for successful venipuncturevenipuncture Three veins in antecubital fossa in order of Three veins in antecubital fossa in order of
selection (1) median cubital (2) cephalic (3) selection (1) median cubital (2) cephalic (3) basilicbasilic
Phlebotomy Technique Phlebotomy Technique ErrorsErrors
Venous Access DifficultiesVenous Access Difficulties Obstructed, hardened, scarred veinsObstructed, hardened, scarred veins Veins difficult to locateVeins difficult to locate Use of Alternative sitesUse of Alternative sites
Top of hand/Side of wristTop of hand/Side of wrist
Vein CollapseVein Collapse Use of appropriate needle size Use of appropriate needle size Smaller evacuated collection tubeSmaller evacuated collection tube
Phlebotomy Technique Phlebotomy Technique ErrorsErrors
Site SelectionSite Selection Avoid sites with IVAvoid sites with IV
Use alternative arm or draw below IV to avoid Use alternative arm or draw below IV to avoid contamination/dilution from IVcontamination/dilution from IV
Document arm if IVDocument arm if IV
Mastectomy—avoid site due to lymphostasisMastectomy—avoid site due to lymphostasis Infection risk/alteration in body fluids and blood Infection risk/alteration in body fluids and blood
analytesanalytes
Edematous areasEdematous areas — —avoid due to avoid due to accumulation of body fluidsaccumulation of body fluids Possible contamination/dilution of specimenPossible contamination/dilution of specimen
Phlebotomy Technique Phlebotomy Technique ErrorsErrors
Tourniquet ApplicationTourniquet Application Tourniquet tied too close to the venipuncture Tourniquet tied too close to the venipuncture
site can cause hematomasite can cause hematoma Veins may not become prominent if Veins may not become prominent if
tourniquet is tied too high (more than 3 to 4 tourniquet is tied too high (more than 3 to 4 inches above venipuncture siteinches above venipuncture site))
Tourniquet left on longer than one minute Tourniquet left on longer than one minute can result in hemoconcentration, affecting can result in hemoconcentration, affecting some test resultssome test results Tourniquet should be released as soon as needle is Tourniquet should be released as soon as needle is
in the lumen of the vein and blood flow establishedin the lumen of the vein and blood flow established
Phlebotomy Technique Phlebotomy Technique ErrorsErrors
Cleansing of venipuncture siteCleansing of venipuncture site Thorough cleaning with alcohol Thorough cleaning with alcohol Allow alcohol to dry completely to avoid Allow alcohol to dry completely to avoid
stinging sensation upon needle entry and stinging sensation upon needle entry and hemolysis of samplehemolysis of sample
Samples such as blood cultures should be Samples such as blood cultures should be collected using iodine to cleanse site to collected using iodine to cleanse site to ensure sterility of sampleensure sterility of sample
Recollection rate for blood cultures ranges due to Recollection rate for blood cultures ranges due to contamination is as high as 50% in hospitals with contamination is as high as 50% in hospitals with increased costs, patient overtreatmentincreased costs, patient overtreatment
Test Collection ErrorsTest Collection Errors Order of DrawOrder of Draw
Order of draw affects the quality of the sample Order of draw affects the quality of the sample and can lead to erroneous test results due to and can lead to erroneous test results due to contamination with the additive from the contamination with the additive from the previous blood collection tubeprevious blood collection tube
HemolysisHemolysis Blood collected insufficient to amount of additive in Blood collected insufficient to amount of additive in
tube, tube, Traumatic venipunctureTraumatic venipuncture Blood collected from area with hematomaBlood collected from area with hematoma Vigorous shaking of tubes after collectionVigorous shaking of tubes after collection Milking the site when collecting capillary samples and Milking the site when collecting capillary samples and
blood collected using a small diameter needleblood collected using a small diameter needle. .
Order of Specimen Order of Specimen CollectionCollection
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
Test Collection ErrorsTest Collection Errors
Timing of CollectionTiming of Collection Timed DrawsTimed Draws Therapeutic Drug MonitoringTherapeutic Drug Monitoring
Peak and trough collection timesPeak and trough collection times Basal State Collections Basal State Collections
Fasting requirements—no food or liquid Fasting requirements—no food or liquid except waterexcept water
Specimens affected by time of day, for Specimens affected by time of day, for example, cortisolexample, cortisol
Test Collection ErrorsTest Collection Errors
Collection tube not completely filledCollection tube not completely filled Example— Incomplete filling results in Example— Incomplete filling results in
specimen dilution and erroneous specimen dilution and erroneous Prothrombin and aPTT test resultsProthrombin and aPTT test results
Test Collection ErrorsTest Collection Errors Capillary Collections—finger stick or heel Capillary Collections—finger stick or heel
stickstick Appropriate siteAppropriate site
Heel stick—sides of the bottom surface of the heelHeel stick—sides of the bottom surface of the heel Finger stick—third or fourth fingers, perpendicular Finger stick—third or fourth fingers, perpendicular
to fingerprint lines on fleshy pads on finger surfaceto fingerprint lines on fleshy pads on finger surface Warming—Warm before collection to increase Warming—Warm before collection to increase
capillary blood flow near skin surfacecapillary blood flow near skin surface Cleaning—cleanse site with alcohol and allow Cleaning—cleanse site with alcohol and allow
to air dryto air dry
Capillary CollectionsCapillary Collections
Massaging site to increase blood flowMassaging site to increase blood flow Milking site can cause hemolysis or tissue Milking site can cause hemolysis or tissue
fluid contaminationfluid contamination Finger sticks—roll fingers toward fingertip at Finger sticks—roll fingers toward fingertip at
11stst finger joint several times finger joint several times Heel sticks—gently squeeze infant’s heel Heel sticks—gently squeeze infant’s heel
before performing puncture. before performing puncture. Perform puncture while firmly squeezing Perform puncture while firmly squeezing
finger or heelfinger or heel Wipe away first two drops of bloodWipe away first two drops of blood
Ensure that full blood drop wells up each Ensure that full blood drop wells up each timetime
Capillary CollectionsCapillary Collections
Avoid touching capillary collection Avoid touching capillary collection tube or micro collection tube to skin or tube or micro collection tube to skin or scraping skin surfacescraping skin surface Contaminates puncture siteContaminates puncture site Blood may become hemolyzedBlood may become hemolyzed
Mixing micro collection tubes with Mixing micro collection tubes with additive frequently to avoid micro clotsadditive frequently to avoid micro clots
Collecting tubes with additives firstCollecting tubes with additives first Protecting tubes for bilirubin from Protecting tubes for bilirubin from
lightlight
Specimen Transport Specimen Transport ErrorsErrors
TimingTiming Some specimens must be transported Some specimens must be transported
immediately after collection, for immediately after collection, for example Arterial Blood Gases example Arterial Blood Gases
Specimens for serum or plasma Specimens for serum or plasma chemistry testing should be chemistry testing should be centrifuged and separated within two centrifuged and separated within two hourshours
Transport ErrorsTransport Errors TemperatureTemperature
Specimens must be transported at the Specimens must be transported at the appropriate temperature for the required appropriate temperature for the required testtest
On ice—ABGs, AmmoniaOn ice—ABGs, Ammonia Warmed --98.6 degrees (37 C), cryoglobulinsWarmed --98.6 degrees (37 C), cryoglobulins Avoid temperature extremes if transported Avoid temperature extremes if transported
from via vehicle from other collection sitefrom via vehicle from other collection site Transport ContainerTransport Container
Some samples need to be protected from light, for Some samples need to be protected from light, for example, bilirubinexample, bilirubin
Transport in leak-proof plastic bags in lockable Transport in leak-proof plastic bags in lockable rigid containersrigid containers
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
Tests ReferredTests Referred0101stst Jan 2013-30 Jan 2013-30thth
June 2013June 2013OPD 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
Total Number of ErrorsTotal Number of Errors
OPD and Wards: 196405 (41%)OPD and Wards: 196405 (41%)
The Errors!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
Causes, Probable (?)Causes, Probable (?)
Improper mixingImproper mixing Labeling by junior/untrained staffLabeling by junior/untrained staff Sample ordering system operated by Sample ordering system operated by
Nursing staffNursing staff Sample transport to lab by wards Sample transport to lab by wards
boys/ayasboys/ayas Lack of knowledge about sampling Lack of knowledge about sampling
requirements in PGT’srequirements in PGT’s
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
phase31.6% 23% 13.3% 13.3% 16% 31% 19%
Postana-
lytical
phase
30.8% 24% 30% 18.5% 9% 12.5% 15%
Multiple
phases6 % 12.5% 6%
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
Error PreventionError Prevention Phlebotomy EducationPhlebotomy Education
Phlebotomists should undergo thorough on-the-Phlebotomists should undergo thorough on-the-job training under the supervision of a senior job training under the supervision of a senior phlebotomistphlebotomist
Continuing EducationContinuing Education Phlebotomists should participate in regular Phlebotomists should participate in regular
educational competency assessments (written educational competency assessments (written and observational) and observational)
Phlebotomy StaffingPhlebotomy Staffing Adequate staffing to maintain collection Adequate staffing to maintain collection
standardsstandards Technology Technology
Use of barcode scanners for patient identificationUse of barcode scanners for patient identification
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).
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
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.
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.
DiscussionDiscussion
How are pre-analytical errors prevented How are pre-analytical errors prevented in your laboratory?in your laboratory?
What do you do to prevent human error?What do you do to prevent human error? What systems does your hospital use to What systems does your hospital use to
prevent errors by non-laboratory staff prevent errors by non-laboratory staff collecting blood?collecting blood?
What pro-active improvements would What pro-active improvements would reduce the number of pre-analytical reduce the number of pre-analytical errors? errors?
Questions?Questions?