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
 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

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

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 errors
 Pre (32-75%)- and post-analytical errors are
estimated to constitute 90% of errors

Clinical Chemistry 53:7 1338–1342 2007
Errors in the Total Test Process
Pre-analytical
Analytical
Post-analytical
62%
23%
15%

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
 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 rubber-
banded to tubes
 Collection tube labels not affixed to all tubes
 Specimen collection tubes labeled insufficiently

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

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

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

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
 Recollection rate for blood cultures ranges due to contamination is as
high as 50% in hospitals with increased costs, patient overtreatment

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.

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

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

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
 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

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 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
 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
Total
67566
53700
33764
16725
7608
5862
7664
192889
828
1015
456
857
208
-
152
3516

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

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%

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
 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

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.

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?

Questions?