‫مشروع إعتماد معمل الكمياء‬
‫اإلكلينيكيه – مستشفى الطوارئ‬
Role of clinician in lab
result accuracy
Prof/Azza abd al baky
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—testing results transmission,
interpretation, follow-up, retesting.
Pre-analytical errors
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Pre- and post-analytical errors are estimated to
constitute 90% of errors
Errors at any stage of the collection, testing and
reporting process can potentially lead to a
serious patient misdiagnosis
Errors during the collection process are not
inevitable but can be prevented with a
diligent application of quality control, continuing
education and effective collection systems.
The steps of the preanalytical
phase
Preparation prior to
sampling
Sampling/handling
Storage/transport
Preparation prior
to analysis
Implications of errors
• Errors made in the
period prior to the
analysis of the
sample ...
• may influence the
quality of the
final measured
results ...
 and
compromise
the diagnosis
and treatment
of the patient
No result is better than bad result
Complex and labor intensive
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The more steps involved in a process, the more
likely there will be errors committed
32 - 75% of all test errors occur in the
preanalytical phase
Stankovic 2008
“Quality Improvements in the Preanalytical Phase:
Focus on Urine Specimen Workflow”
Effects of Pre-analytical Variables on the
Quality of Laboratory Testing

Paying close attention to the preanalytical
variables associated with blood collection is
critical in ensuring accurate test results in
all areas of the clinical laboratory.
The Pre-Analytical process

Patient Identification
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Sampling Technique

Test Collection Procedures

Specimen Transport

Specimen Processing
The Pre-Analytical process
Collect Sample:
 Locate Patient
 Prep Patient
 Draw Sample
 Label
 Dispose of supplies
Patient identification
When identifying the patient, have them
provide their full name, address, identification
number and/or date of birth. Hospital No
inpatients should be wearing an identification
band with the above information, which the
phlebotomist should confirm before the
venipuncture.
Effects of Pre-analytical Variables on the
Quality of Laboratory Testing

Patient Identification: It is important to identify
a patient accurately so that blood is collected
from the correct person. Drawing blood from
the wrong person, or labeling the correct
patient’s sample with a different patient’s label
can certainly contribute to laboratory error.
(Mislabeling ???)
Factor affecting lab result

Some patient variables that affect test results
Age
Gender
Diet
Drugs
Exercise
Posture
Haemolysis,lipemia
& icterus
Genetic variation
Nutrition status
Diagnostic and therapeutic
procedures(PR&endoscopy)
Obesity
Biorythm
Special habits
Test Collection

Timing of Collection
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Therapeutic Drug Monitoring

Peak and trough collection times
Basal State Collections
 Fasting requirements—no food or liquid except
water(10-12h)
 2h postprandial, from the start of food .
 Specimens affected by time of day, for example,
cortisol, iron and TSH.
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Phlebotomy
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Phlebotomy is a highly complex skill requiring
expert knowledge, and critical judgment
venipuncture is a frequent medical procedure.
Phlebotomy errors may cause harm to patients
or result in needle stick injury to the
phlebotomist
Error Prevention

Phlebotomy Education
Phlebotomists should have completed a standard
academic course in phlebotomy and 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)
 Professional Licensure
Phlebotomy Staffing
 Adequate staffing to maintain collection standards
Technology
 Use of barcode scanners for patient identification
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1-posture:
The patient should be comfortably seated or supine for 20
minutes before sampling.Not standing
The patient 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.
Avoid the arm with:
Extensive scarring or hematoma .,infection , edema ,burn ,
Containing I.V. access for I.V. infusion.
On the side of mastectomy.
Phlebotomy Technique

Correct collection system
Evacuated tube system (Vacutainer) for large veins
in antecubital fossa
 Syringe for small, fragile veins or veins outside
antecubital fossa
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Venous access
Needle entry should be at 15 to 30 degrees
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

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
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Phlebotomy Technique

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
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Test Collection
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Additive : EDTA,citrat, lithium heparin
,oxalate,flourid
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.
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Test Collection
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Capillary Collections—finger stick or heel stick
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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
 Discard first drop of blood.

Recommended order of draw (NCCLS):
1. Blood Culture Bottles (Aerobic-Anaerobic)
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

Correct Specimen Volume: All blood collection
tubes need to be filled to the correct volume. This
will ensure the proper amount of blood for the
amount of additive in the tube (blood to additive
ratio). For example, if a 5 mL draw heparin tube is
only filled with 3 mL of blood, the heparin
concentration is erroneously high and may
potentially interfere with some chemistry analytes,
tube for Coagulation Studies incomplete filling
results in specimen dilution and erroneous
Prothrombin and aPTT test results.

Proper Tube Mixing: All tubes with additives
need to be inverted to mix the additive evenly
with the blood. Improper mixing of the
tube after venipuncture could contribute to
sample clotting.
E) Specimen transport
Temperature
Light
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 -- (37 C), cryoglobulins
 Avoid temperature extremes if transported 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 ,avoid agitation.
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Blood Specimen Transport
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Transport of blood specimens in the proper
manner after collection ensures the quality of
the sample
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

Special Handling of Blood Specimens:
Certain chemistry analytes will require the
tube of blood to be chilled after collection in
order to maintain the stability of the analyte.
A slurry of ice and water is recommended for
chilling the tubes of blood. Examples :
adrenocorticotropic hormone (ACTH),
angiotensin converting enzyme (ACE),
acetone, ammonia, catecholamines, free fatty
acids, lactic acid, pyruvate and renin ,PTH
Blood gases analysis
“Collection of a blood specimen, as well as its handling
and transport, are key factors in the accuracy of clinical
laboratory analysis and ultimately in delivering quality
patient care”
”Arterial blood is one of the most sensitive of the
specimens sent to the clinical laboratory for analysis”
”Blood gas and pH analysis has more immediacy
on patient care than any other laboratory
determination”
”In blood gas and pH analysis an incorrect
result can often be worse for the patient
than no result at all”
What is so special about blood
gases?
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NOT like other blood samples
STAT parameters
 Short Turn Around Time
 Must be analyzed within a
short time
 pO2, pCO2, pH, LAC, GLU
Valuable results right now
 Not in one hour
Sample composition changes
Patient status changes
Some points to keep in mind
- sampling from A-lines
Preparation prior
to sampling
Sampling/handling
• Label the sampler with patient ID
• Use dry electrolyte balanced heparin
• Endeavor to keep the patient’s
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 and hemolysis
• Expel any air bubbles immediately after
sampling
• Mix the sample thoroughly with
heparin after sampling
Storage/transport
Preparation prior to
sample transfer
• Analyze sample immediately
• If storage is unavoidable,
store the sample at room
temperature for max. 30 min.
Samples with expected high
pO2 values should be analyzed
within 5 min.
• Before transferring the
sample into the analyzer mix
thoroughly
• Visually inspect the sample
for clots and air bubbles
• Enter patient ID in analyzer
logs
Stabilization of the respiratory condition
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To get a true picture of the
patient’s respiratory condition
the patient should ideally be in a
steady state of ventilation
Patients should be at rest for
5 min
Ventilatory settings should be
unchanged for 20 min
Pain and anxiety from arterial
puncture may influence the
steady state of respiration
and should thus be minimized
Storage recommendations
General storage recommendation
Do not cool the sample
Analyze within 30 minutes

For samples with high pO2
Analyze within 5 minutes
For special studies, e.g. shunt
Analyze within 5 minutes
For samples with high leukocyte or
platelet count
Analyze within 5 minutes
Expected delayed analysis
When analysis is expected to be
delayed for more than 30 minutes, the
use of glass syringes and storage in
ice slurry is recommended
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Storage and transport time
should be kept at a minimum
Volatile nature of gases
Continued metabolism in
blood
For parameter panels including
GLU/LAC, be aware that 30
minutes storage might lead to
biased results
It is recommended by the
NCCLS to avoid cooling of
samples when kept in plastic
Continued cellular metabolism in sample
pO2
since oxygen will still be consumed
pCO2
since carbon dioxide will still be produced
pH
primarily due to the change in pCO2 and
glycolysis
cCa2+
since the change in pH will
binding of Ca2+ to protein
cGlu
since glucose will be metabolized
cLac
due to glycolysis
influence the
Slowing down the metabolism
pO2

Time
0-4 C
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25 C
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Blood gas samples in glass
samplers can be cooled
Storing the sample at a lower
temperature (0-4 °C) will slow
down the metabolism by at least
a factor of 10 [NCCLS]
Cool samples in an ice
slurry or other suitable coolant
Never store the samples
directly on ice as this
causes hemolysis of the
blood cells
NCCLS Document C27-A; Blood Gas Pre-Analytical Considerations: Specimen Collection, Calibrations and Controls; Approved Guideline
Potential preanalytical errors
Preparation prior
to sampling
• Missing or wrong patient/sample
identification
• Use of the wrong type or amount of
anticoagulant
- dilution due to the use of liquid
heparin
- insufficient amount of heparin
- binding of electrolytes to heparin
• Inadequate stabilization of the
respiratory condition of the patient
• Inadequate removal of flush solution in
a-lines prior to blood collection
Sampling /handling
Storage and transport
Prep prior to transfer
• Mixture of venous and
arterial blood during
puncturing
• Air bubbles in the sample
• Insufficient mixing with
heparin
• Incorrect storage
• Hemolysis of blood cells
• Visually inspect the sample
for clots
• Inadequate mixing of sample
before analysis
• Failure to identify the sample
upon analysis
Mixture of venous and arterial
blood
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Vei
n
Arter
y
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40 mmHg / 5.3 kPa
100 mmHg / 13.3 kPa
When puncturing an artery it is
important not accidentally to get
the arterial blood mixed with
venous blood
This may, for instance, occur, if
you hit a vein before locating
the artery
Even an admixture of a small
amount of venous blood may
significantly bias the results
This is especially true of pO2
and sO2, but other parameters
may also be affected
Mixture of venous and arterial
blood
Vein:
Pressure rarely
> 10 mmHg
Artery:
Systolic blood
pressure normally
> 100 mmHg
 In
arteries the blood
pressure is high enough
to fill a self-filling
syringe
 If a self-filling syringe
does not fill it may be
because a vein has been
hit
 In that case a new
sample should be taken
Inadequate removal of flush
solution
Flush solutions used in alines must be removed
completely from the system
to avoid a dilution of the
blood sample
 It is recommended to
withdraw a volume equal to
three to six times the “dead
space” of the catheter
system (NCCLS)
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Inadequate removal of flush
solutions
Sample
B and A are both a-line samples taken from the same patient
immediately after each other
Before taking sample B only 1 mL of saline solution was removed - the
tubing, however, looked red
Before taking sample A saline solution was removed as recommended
Sample A
Sample B
ctHb
cGlu
cK+
cNa+
cCa2+
cClpH
pCO2
pO2
ctHb
cGlu
cK+
cNa+
cCa2+
cClpH
pCO2
pO2
6.2 mmol/L
9.6 mmol/L
3.8 mmol/L
130 mmol/L
1.00 mmol/L
101 mmol/L
7.271
50.5 mmHg / 6.7 kPa
116.7 mmHg / 15.56 kPa
4.6 mmol/L
6.9 mmol/L
2.5 mmol/L
137 mmol/L
0.61 mmol/L
113 mmol/L
7.275
35.9 mmHg / 4.8 kPa
129.3 mmHg / 17.2 kPa
Air bubbles
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Any air bubbles in the sample
must be expelled as soon as
possible after the sample has
been drawn
before mixing the sample with
heparin
before any cooling of the
sample
Even small air bubbles may
seriously affect the pO2 value of
the sample, normally resulting in
increased values
An air bubble whose relative
volume is 0.5 to 1.0 % of the
blood in the syringe is a
potential source of a significant
error
Effect of air bubbles - an example
 Sample
A and B were taken from the same patient
immediately after each other
 Sample A without air bubbles was analyzed
immediately after collection
 100 µL air was added to sample B (1 mL). It was stored
cold (0-4 °C) for 30 minutes and mixed for 3 minutes
before sample analysis
Sample A
pO2 288.6 mmHg / 38.5
kPa
(FIO2 1.000)
Sample B
pO2 253.3 mmHg / 33.8
kPa
(FIO2 1.000)
Insufficient mixing with heparin
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Insufficient mixing can
cause coagulation of the
sample
It is recommended to
mix the blood sample
thoroughly with heparin
Invert the syringe 10
times and roll it between
your palms
Inadequate mixing - an
example
 Sample
A and B were taken from the same patient
immediately after each other and stored cold for
10 minutes
 Sample A was mixed in a rotator (14
revolutions/min) for 3 minutes
 Sample B was mixed in a rotator (14
revolutions/min) for 1 minute
Sample A
ctHb 6.2 mmol/L
Sample B
ctHb 4.5 mmol/L
Hemolysis of blood cells

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The blood cells are relatively
fragile, and therefore hemolysis
may easily occur during blood
sampling
Hemolysis may, for instance, occur
due to
 high filling pressure through
a narrow entrance (e.g. during
too vigorous sample aspiration,
sample transfer to the analyzer,
etc.)
 vigorous rubbing or squeezing
of the skin during capillary
sampling
 too vigorous mixing of the
sample
 cooling down the sample
below 0 °C
“The weak link”
Blood gas analyzers of
today are highly accurate
 Make sure that sample
represents patient status
 The preanalytical phase is
the weak link in the
Patient Focus Circle
 Many potential errors
 Can be overcome by
Training
User guidelines
Sampling products

Specimen Quality Markers for
Rejection
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Clotted
Hemolyzed
Underfilled, overfilled
Insufficient quantity
Incorrect labeling
Unlabeled specimen
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Incorrect patient
Incorrect specimen
Contaminated
Lost sample
Too old to process
Broken and leaking
Finally…
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The human role in sample collection makes
complete elimination of errors associated
with laboratory testing unrealistic
However, good practices and compliance
with the new strategies for error prevention
can lead to a substantial reduction in preanalytical errors.