A. Purpose of examination
ESR is a useful nonspecific test of inflammatory response to tissue injury, as in diseases like, Rheumatic arthritis, tuberculosis, multiple myeloma, temporal arteritis, polymyalgia rheumatica. Conventional manual ESR method is simple, cheap and not dependent on power supply. Suitable for point of care (near patient) testing. Prognostically important in Hodgkin’s disease, renal cell carcinoma.
B. Principle of examination
When well mixed venous blood is placed in a vertical tube ,erythrocyte will tend to fall toward the bottom .The length of fall of the top of the column of erythrocyte in a given interval of time is erythrocyte sedimentation rate.
C. Performance specifications
Not applicable.
D. Sample type required
Anticoagulated Whole blood- Citrated or EDTA whole blood
E. Preservatives needed
ESR is to be performed within 6 hrs of collection & if needed stored at 2’C-8’C after analysis for 24 hrs.
F. Reagents required
3.8% Sodium citrate
G. Calibration method.
Not applicable.
H. Detailed work bench instruction of ESR / programming steps
• ESR cup =0.5ml sodium citrate+2ml EDTA whole blood
• Westergren pipette is filled to 0 mark
• Pipette placed vertical in the rack at R.T.
• After 60 minute distance from 0 mark to top of the column of red cells is recorded in mm as ESR value. When a sample for ESR examination arrives at the laboratory section of NCHSLS, it is received, performed as per SOP common for various examinations describes in this manual.
I. Quality control procedure :
Daily one random patient sample is checked by manual method (Modified Westergrene) and automated method. Results of comparison are recorded in HI: C\records\file\9\Internal quality control records.
J. Interferences.
a. Increase anticoagulant– increase ESR
b. Heparin—alters zeta potential
c. Bubbles in tube
d. Hemolysis
e. Tilting of tube
g. High temperature
h. Timing—with in 2hr,pref.4hrs(12hrs if at 4*c)
i. Clinical—age, menstruation, medications
K.Calculation of results and uncertainty: Not Applicable
L.Biological reference interval:
| Males | ESR | Females | ESR | Pregnant | ESR |
|---|---|---|---|---|---|
| 0-50 yr | <10 | 0-50 yr | <12 | First Half of Preg | < 48 |
| 51-60 yr | <12 | 51-60 yr | <19 | Second Half of Preg | <70 |
| 61-70 yr | <14 | 61-70 yr | <20 | ||
| >70 yr | 30 | > 70 yr | About 35 | ||
M. Reportable interval for examination results: 1- 150 mm/hr
N. Critical values
| Stroke | >= 28 |
| Prostatic cancer | >= 37 |
| CAD | >22 |
| Metastasis | >100 |
| Temporal arteritis | >90 |
O. Interpretation by the laboratory
P. Potential sources of variability
Preanalytical sources of variability: Delayed sample receipt, Leucocytosis, Leukemia, Septicemia, short draw in vacuum tube.
1.Difference in specific gravity between red cells and plasma.
2.Extent to which red cells form rouleaux ,which sediment more rapidly than single cells.
3.Ratio of red cells/plasma(PCV).
4.Plasma viscosity.
5.Verticality of the sedimentation tube.
6. Bore of the tube.
7. The dilution (if any) of the blood.