Q: My 6 months old son had high fever and had to be admitted to the hospital for 2 days. His blood report revealed an ESR of 40%. He recovered from it but now the temperature has risen again. Could you please educate me on ESR count? Why does it rise and how do we control it?

A:The Erythrocyte Sedimentation Rate (ESR) is not a count but a test that measures the distance that red blood cells have fallen after one hour in a vertical column of anti coagulated blood under the influence of gravity and is measured in millimetres per hour. It is a very non-specific indicator of the presence of disease - i.e., it doesn't point to any one particular illness but to a variety of possibilities. In certain illnesses, the red blood cells become coated with a layer of protein which makes them stick together in columns and fall faster down the tube (giving a higher result on the test). Although many studies have been done, an increased ESR remains a non-specific finding. The use of the ESR as a screening test in asymptomatic persons is limited by its low sensitivity and specificity as it is affected by many variables. Women tend to have higher ESR values, as do the elderly. Obese people too tend to have raised ESR for some unknown reason though this is not thought to have any clinical significance. The amount of fibrinogen (a blood protein) in the blood directly correlates with the ESR. Any condition that increases fibrinogen levels (e.g., pregnancy, acute infection, diabetes mellitus, end-stage renal failure, heart disease, collagen vascular diseases, malignancy, and chronic infection) may elevate the ESR. An elevated ESR in the absence of other findings should not prompt an extensive laboratory or radiographic evaluation but a mild to moderately raised one without any obvious cause should be repeated after a few months rather than a making an expensive search for occult disease. As much more specific tests are now available for most of the diseases that cause a rise in ESR, the role of this test is very limited now.