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I wish to share with the readers the results of a study carried out to ascertain if there is a need to measure erythrocyte sedimentation rate (ESR) only on a fasting blood sample. From undergraduate physiology days down to the years of clinical medicine it was taught that ESR should be done on a fasting blood sample. The reason being that food in some way increases the ESR. However, nowhere in pathology literature is spelt out the need of fasting ESR, nor is there mention of the difference between a fasting, post-prandial (PP) or a random ESR.
Eighty personnel and their families (all adults), who were undergoing a fasting and post-prandial blood sugar test were simultaneously investigated for ESR. Majority of these patients had either obesity, diabetes, IHD or hypertension. The fasting and post-prandial samples were taken either after a normal breakfast or after 75 g of glucose. The ESR was measured by the Wintrobes and Landberg's method .
The average ESR on a fasting blood sample was 22.77 ± 19.18 mm fall at the end of one hour whereas it increased to 28.41 ± 19.11 mm fall after glucose or breakfast. Standard error of difference between the two means did not show the result to be statistically significant (SE=3.026).
The phenomenon of erythrocyte sedimentation has been exhaustively investigated [2,3]. The rate of fall of the red cells in influenced by a number of interacting factors. Basically it depends upon the difference in specific gravity between red blood cells and plasma, but the actual rate of fall is influenced greatly by the extent to which the red cells form rouleaux which sediment more rapidly than single cells. Other factors which affect sedimentation include the ratio of red cells to plasma (i.e. the packed cell volume), and the plasma viscosity. The all-important rouleaux formation is mainly controlled by the concentrations of fibrinogen and other acute phase proteins e.g. haptoglobin, α-antitrypsin and C reactive proteins.
The test is widely used in clinical medicine but is empirical . ESR is increased in most infections, anemias, and conditions associated with hyperglobulinemia and hypercholesterolemia. The rate is decreased in polycythemia, congestive failure and sometimes in iron deficiency anemia. An increased ESR is always abnormal whereas normal ESR indicates health or mild disease. Thus the test helps to differentiate an organic disease from functional one.
In the defence services, the ESR is usually done on a fasting blood sample, though the manual on laboratory methods does not specify so .
The results do not suggest that the ESR may be influenced to such an extent as to cause a significant difference. It points to a need for review of the policy to do a fasting ESR only. It is therefore suggested that a much larger study be taken up at a large hospital where ESR in various subgroups of patients can be done and results can prove conclusively the need or otherwise of ESR to be done on a fasting sample.