Pre-analytical Laboratory
Errors
Dr Sami Saeed
Associate Professor/HOD
Foundation University Medical College
Path Lab, Fauji Foundation Hospital,
Rawalpindi
Email: drsami@comsats.net.pk
Objectives
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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 preanalytical errors associated with blood collection
and transport
Introduction
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Three phases of laboratory testing:
pre-analytical, analytical and post-analytical
Pre-analytical—specimen collection, transport
and processing
Analytical—testing
Post-analytical—results transmission
Pre Analytical Phase
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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
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Some such as specimen variables can be
controlled
Knowledge of uncontrollable variables need to
be well understood
Pre Analytical Phase
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
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
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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 errors

Pre (32-75%)- and post-analytical errors are
estimated to constitute 90% of errors
Errors in the Total Test Process
23%
15%
62%
Pre-analytical
Analytical
Post-analytical
Clinical Chemistry 53:7 1338–1342 2007
Types of Errors

Patient Identification

Phlebotomy Technique

Test Collection Procedures

Specimen Transport

Specimen Processing
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
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
Patient Complications

Some patient variables that affect blood
specimens

Diet

Fasting
Exercise
 Obesity
 Allergies to alcohol or iodine used to clean
venipuncture site
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Use alternative cleanser such as chlorhexidine
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 rubberbanded to tubes
 Collection tube labels not affixed to all tubes

Specimen collection tubes labeled insufficiently
Phlebotomy Errors
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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
Phlebotomy Technique Errors

Phlebotomy technique is important
Ensures test result validity
 Minimizes trauma to patient
 Minimizes potential for phlebotomist injury
 Reduces recollections
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Vein selection essential for successful
venipuncture

Three veins in antecubital fossa in order of selection
(1) median cubital (2) cephalic (3) basilic
Phlebotomy Technique Errors
 Venous
Access Difficulties
 Obstructed,
hardened, scarred veins
 Veins difficult to locate
 Use of Alternative sites

 Vein
Top of hand/Side of wrist
Collapse
 Use
of appropriate needle size
 Smaller evacuated collection tube
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
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
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

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Recollection rate for blood cultures ranges due to contamination is as
high as 50% in hospitals with increased costs, patient overtreatment
Test Collection Errors
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Order of Draw
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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
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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.
Order of Specimen Collection
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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 Errors

Timing of Collection
Timed Draws
 Therapeutic Drug Monitoring
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Basal State Collections
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Peak and trough collection times
Fasting requirements—no food or liquid except water
Specimens affected by time of day, for example,
cortisol
Test Collection Errors

Collection tube not completely filled

Example— Incomplete filling results in specimen
dilution and erroneous Prothrombin and aPTT test
results
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

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
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
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

Transport Errors
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Temperature
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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
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Transport Container
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Some samples need to be protected from light, for example,
bilirubin
Transport in leak-proof plastic bags in lockable rigid
containers
Physiological Pre Analytical
Variables
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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
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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 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
Total Number of Errors
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OPD and Wards: 196405 (41%)
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
67566
53700
33764
16725
7608
5862
7664
828
1015
456
857
208
152
Total
192889
3516
Causes, Probable (?)
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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
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)
Preanalytical
phase
31.6%
53%
55.6%
68.2%
75%
44%
60%
Analytical
phase
31.6%
23%
13.3%
13.3%
16%
31%
19%
Postanalytical
phase
30.8%
24%
30%
18.5%
9%
12.5%
15%
Multiple
phases
6%
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 Prevention
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Phlebotomy Education
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Continuing Education
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Phlebotomists should participate in regular educational
competency assessments (written and observational)
Phlebotomy Staffing
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Phlebotomists should undergo thorough on-the-job training
under the supervision of a senior phlebotomist
Adequate staffing to maintain collection standards
Technology

Use 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 nonhemolyzed 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
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In OPD, blood was collected with the application
of tourniquet and fist clenching
In the ward, blood was collected through an indwelling 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
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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.
Discussion
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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?
Questions?