Example
SOP
ERYTHROCYTE
SEDIMENTATION RATE (ESR)
WESTERGREN
METHOD
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A
– 001
Page
1 |
Authorised
signature: |
Issuing
Date: April 12, 2000
Next
Revision Date: April 12, 2001
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Staff
able to perform test:
Laboratory Assistant and higher |
Principle
of the Test Method
The ESR expresses in mm per hour the rate at which
red blood cells settle when anti-coagulated blood is allowed to
stand in a narrow tube (Westergren).
It is shown by the height of the column of clear plasma at
the end of one hour. |
Clinical
Significance of the Test:
ESR is used as a screening method for all disease
that are associated with a modification
of the plasma proteins like globulin, albumin and fibrinogen.
ESR is not a very reliable screening method as it can be
raised when there is no disease and can be normal when disease is
present. It also does not indicate the type of disease. |
Specimen:
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Equipment
Requirements:
-
Westergren
rack
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Westergren
tubes, internal diametre 2.5mm
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Dilution
bottles to hold 2 ml (4 volumes of blood/1 volume of anticoagulant
diluent solution)
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Timer
(1hour)
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Reagents & Stain Requirements:
Preparation of 3.8% Tri-sodium Citrate
Solution
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Tri-sodium
Citrate, anhydrous ......................................... 3.8
g
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Distilled
water........................................................
up to 100
ml
Important:
Keep the solution in the refrigerator.
If the solution is cloudy or contains particle discard and
prepare a fresh solution!
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Test
Procedure Instructions:
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Draw 2ml
of venous blood and immediately place 1.6 ml into the
Trisodium citrate solution. Note: You can also use EDTA
blood. If kept at 4°C, it can be used after up to 24
hours. In this case mix the EDTA blood well, and place 1.6
ml into the Tri-sodium citrate solution.
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Wipe the outside of the Westergren tube with a
tissue.
-
Make
sure no air bubbles enter the tube.
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Recheck that the tube is filled up to the 0 mark,
exactly.
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Reporting
and Interpretation of Results:
Normal
Value: Male:
1 - 10 mm /hour
Female:
3 - 14 mm /hour
Increased Values of ESR:
Are found with
all diseases associated with a modification of the plasma proteins
like globulin, albumin and fibrinogen.
ESR shows especially high values in:
Special Note: (While
reading the result you should also pay attention to the following:)
The colour of
the plasma:
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Dark
yellow , indicates Hepatitis
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Clear
as water, indicates lack of iron
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White
and turbid, indicates Nephrosis, Diabetes, Lipaemia.
The layer of
white blood cells just above the red cells:
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Internal
Quality Control Procedures and Sources of Error:
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Correct dilution of blood and Tri-sodium
Citrate Solution
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Store Tri-sodium Citrate Solution in the
refrigerator
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Tri-sodium Citrate Solution should not be
turbid
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Avoid air-bubbles in the Westergren tube
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Place
the Westergren tube in a vertical position
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Temperatures above 23 °C
increase the speed of the ESR, therefore keep the ESR rack at
the coolest place of the lab and out of direct sun light.
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Reference:
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Maurice King, 1973 A Medical Laboratory for Developing
Countries, London, Oxford University Press
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WHO, 1980, Manual of Basic Techniques for a Health
Laboratory. Geneva, WHO
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