QC in coagulation

QUALITY CONTROL IN
HAEMOSTASIS

OUTLINES
Quality-assurance
Types of quality assurance

Quality assurance in the
haematology laboratory is intended
to ensure reliable test results with
the necessary degree of precision
and accuracy.
Accuracy: refers to the closeness
of the estimated value to that
considered to be true.
Precision: refers to the
reproducibility of a result, but a test
can be precise without being
accurate.

Types of quality assurance
 Internal quality control:
Is the set of measure
undertaken by the staff of the
laboratory to ensure quality from
the collection of specimen of the
test up to the analytical result, and
the measure should include test
results on control material.
 Pre-analytic procedure.
 Analytic.
 Post analytic.

 External quality control:
The assessment of result
from assessment produced
at a certain site by comparing
with results obtained by other
sited on the same material
distributed by an external
agency which also analysis
the data statically.
 We need EQC to compare
our performance with other.

 Pre-analytic stage: (collection of sample)
1. Use fullness of the request form:
Sex, Age, Family history, Clinical remarks,
Clinical exam.
2. Patient preparation:
 Pt should be relax about 15 min !
because the excessive stress and excersice
cause change in blood clotting and fibrinolysis
(Increased F V111 and VWF).
 Pt under aspirin administration, should be stop
for 7 days!
Aspirin is block the cyclooxygenase.
 If possible the Pt must be fasting!
To reduce the lipid level, specially when
use automated analysis.

3. Specimen quality control:
(a) Use the venous blood rather than the
capillary blood!
Because capillary blood require
modification of technique, and locally
established normal range.
(b) Proper collection:
 All blood samples must be collected by
personnel who are trained and
experienced in the technique.
 Clean the site of the vein puncture.
 Select A proper Vein.

 Avoid the using of torniquate!
because it causes the venous
occlusion which lead to
haemoconcentration, that is lead
to increase the fibrinolytic activity,
Platelets released and activation
of Co-factor.
 A disposable plastic syringe of a
needle gauge 20-23 is used!
- To avoid the contact
activation.
- To avoid the haemolysis.

4.The anticoagulant use:
 The commonly anticoagulant used
is Tri-Na citrate!
1. The calcium ion is neutralised
more rapidly in citrate.
2. Prevent continued tPA–PA1-1
binding.
 The labile factors (factors V and
VIII) are un-stable in oxalate.

 Heparin and EDTA directly
inhibit the
coagulation process and
interfere with end-
point determinations.
 APTT tests are more
sensitive to the
presence of heparin.

 The recommended volume is 9
vol of blood:1 vol of
anticoagulant, when the PCV
is normal.
Haematocrit Citrate (ml)
0.20 0.70
0.25 0.65
0.30 0.61
0.55 0.39
0.60 0.36
0.65 0.31
0.70 0.27

 Screw capped plastic
containers used for the blood
collection, also can use the
evacuated tube.
 If an evacuated tube system
is used for collecting samples
for different tests, the
coagulation sample should be
the second or third tube
obtained.

5. Right labelling (Pt identification):
Pt identification is very important
both at the bedside and within the
laboratory to avoid the mistakes.
6. Sample transportation:
 The sample delivered quick as
possible to prevent the
deterioration of the labile factors.
 Certain investigation need to put
the sample in crushed ice (urgent
fibrinolytic test).

 Storage of Plasma:
 PT and APTT are carried out on
fresh samples.
 coagulation assays, unless
urgently required, can be
performed in batches at a later
date on deep frozen plasma.
Storage of small aliquots of
samples in liquid nitrogen (–
196°C) is the optimum, although
samples may be frozen at -40°C
or -80°C for several weeks .

Analytic stage
1. Equipment reliability.
2. Reagent stability.
3. Adequate calibration.
4. Quality control material.
5. Good pipetting technique.
6. Good climate.
7. Cleaning of equipment.
8. Procedure using SOPs.

1.Equipment reliability:
 Water baths: A 37°C water bath is
required for manual coagulation
tests,
 Refrigerators and Freezers:
Check that the temperature
 4° ± 2°C for refrigerators.
 -20° ± 2°C for freezers,
 Plastic and Glass Tubes:
 Glass tubes For clotting tests.
 Plastic tubes should be used
for sample dilutions, storage, and
reagent preparation.

 Pipettes:
 A range of graduated glass.
 Automatic pipettes .
The latter should be accurate and
durable
 Centrifugation:
 PPP prepared by centrifugation at
2000 g for 15 min!.
 Sample should kept at RT for PT, LAC
and FV111assay. And in 4°c for other
assay.
 the testing should preferably be
completed within 2 hours of collection

 Stopwatches and Clocks:
At least four stopwatches are
needed for measuring clotting
times and for short incubations.
 Automated Coagulation
Analysers:
If coagulation analysers are used, it
is important to ensure that their
temperature control and the
mechanism for detecting the end-
point are functioning properly.

2. Reagent quality control:
 The focus in the quality control
procedure for ensuring satisfactory
reagents for performing routine
coagulation tests, including : the PT, PTT,
functional fibrinogen level and TT.
 Thromboplastin reagent for PT derived
from bovine and rabbit brain or lung.
 PTT reagent contain two types of
activators:
 Particulate activator: Kaolin, silica.
 Soluble activator: Contain ellagic acid.
Test result depend on the specific
reagent and instrument used.

Reagent selection:
In selecting reagents for use
in laboratory testing several
factors should be considered:
1. Purpose for forming the test.
2. Reagent instrument
compatibility.
3. Reagent cost.
4. Reproducibility.
5. Reagent sensitivity.

Sources of error in coagulation
reagent:
1. from open vials or reagent.
2. Contamination.
3. Storage problems related to
excessive exposure of
reagent to either heat or cold.
4. Deterioration of reagent, by
freezing and thawing.
5. Reconstitution.
6. Expiration date.

3. Calibration:
 Is procedure which uses known
quantities of analyses to adjust the
analytical system to ensure that result
well be accurate.
 types of calibration in coagulation:
 National standard (e.g., National
Institute
for Biological Standards and
Control).
 Commercial standard.
 Normal pool plasma(activity100%
or 1.0 u/ml).
 The principle of calibration is
repetition to minimise possible errors
at each stage of calibration.

4.QUALITY-CONTROL
MATERIALS:
 Types of control material uses:
 PPP.
 Commercially.
 Duplicate Tests on Patients'
Specimens.
 Using the control plasma to
detect the precision.
 Batches must included the
controls
( Normal, abnormal) to detect
the non linearity in STD curve.

 Standard Operating
Procedures :(SOPs)
Standard operating
procedures (SOPS) are
written instructions that are
intended to maintain optimal
consistent quality of
performance in the laboratory

Format for a standard
operating procedure (SOP)
 Cover page .
 Scope .
 Specimen requirements .
 Specimen reception .
 Safety precautions .
 Equipment and reagents .
 Test procedure .
 Reporting.
 Clinical significance .
 Test limitations .
 Maintenance of equipment .
 Specimen storage post test .

Post-analytical stage
1. Accurate recording of result and
interpretation.
2. Speed reporting.
3. Write of normal value in result.
4. Biological validation of result.
5. Conservation of specimen(storage).
6. Proper dispose of waste.
7. Transfer the report to the doctor or
ward.
8. Documentation.

 Some Common “Technical” Errors
1. Faulty collection of the sample.
2.Underfilling or overfilling of the bottle.
3. An unsuitable anticoagulant.
4. Collection of blood through a line that
has at some stage been in contact
with heparin.
5.Contamination of the kaolin.
6. Undue delay in sample analysis.
7.Use of inaccurate pipettes.
8.Machine malfunction.
9.Incorrect waterbath temperature.
10.Calcium chloride at incorrect
concentration or not freshly prepared.

Factors Affecting The
Interpretation Of The Results
I. Biological
II. Physical
III. Chemical
IV. Patient variable

I.Biological
1. Sex
2. Age
3. Diet
4. Time
5. Stress
6. Posture

7-Exercise(30-40% increase in
PLTs count)
8-Medical history
9-Pregnancy
10-Menstrual cycle
11-Drug history
I.Biological

II.Physical
1. Light
2. Temp.
3. Evaporation
4. Atmospheric pressure
5. Altitude
6. Humidity

Time VS Temp.
Time Temp.c˚
2hrs 22-24
4hrs 4
2weeks -20
6months -70

III.Chemical
1. Cell metabolism
2. Proteolysis
3. Cytolysis
4. Additive(EDTA artificially high
PLTs count,Citrate,Heparin)
5. Glycolysis Inhibitor
6. Promoters of clotting

IV.Patient variables
1. Age
2. Weight
3. Diet
4. Smoking
5. Drugs
6. Stress
7. Sex(in women, the PLTs count
20% higher than in men)

1.Age
Increasing age
causes:
a. Increase
procoagulant
proteins(I,V,VII
I,IX)
b. Greater
platelet
aggregation
c. Reduced
fibrinolysis
Newborn
babies
a. Low levels of
factors II,VII,IX,X
,XII,XI.
b. Low levels of
Protein C and
Protein S
c. Prolonged PT
and aPTT
d. Normal levels by
6 months old

Weight
 Male and female may have
different normal ranges of
protein C and protein S.

Diet
Effect
Diet
Adversely affect
warfarin therapy
Foods high in
vitamin K
Reduces PLTs
aggregation
Caffeine
Has no effect
Moderate
consumption of
alcohol
Reduces PLTs
aggregation
Red Wine

Smoking
Increased Decreased
PLTs
count(transient)
Protein S
Fibrinogen
Beta-
thromboglobulin
VWF

Drugs
Effect
Drug
s
dependant
vitamin K
affects
factors(II,VII,IX,X)
Warf
arin
Reduces PLTs
aggregation and
increase the effect of
Warfarin
Aspir
in

Variability of coagulation assays
Within laboratory
1. Dilution error
2. Differences in the
composition of
reagents
3. Failure to take the
time-trend into
account
4. Differences in
experience and
technique between
operators.
Between laboratory
1. Differences in
methods
2. Differences in
the
composition of
reagents

QC in coagulation

QC in coagulation

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