The ESR test
What is an ESR test?
The erythrocyte sedimentation rate test or the ESR test is a non- specific screening test for inflammation anywhere in the body. Also known as the Westergren ESR, it measures the rate of sedimentation of red blood cells in one hour. Inflammation in the body cause increase in abnormal proteins which leads to clumping of red blood cells. This, in turn, will cause them to sink to the bottom at a faster rate.
Why is it conducted?
This is a quick test that helps to identify the presence of inflammation in the body. The ESR test does not clearly isolate the reason for inflammation and is therefore not used for diagnostic purposes. However, it can help to monitor treatment response as it reveals increase or decrease in inflammation. Despite the availability of more specific tests that better help to locate the source of inflammation, the ESR test is still preferred as it is more cost effective.
Who should go for it?
This test is often requested in conjunction with or followed by other tests. It is frequently ordered in the following situations.
- Persons who have fever for which there may not be an obvious explanation.
- People suffering from muscle pain, especially that of large muscles and Polymyalgia rheumatic is suspected.
- An ESR test can also be requested if rheumatoid arthritis is suspected.
- Persons with unclear symptoms are advised this test to check the possibility of infection.
- Persons suffering from autoimmune disorders like, allergic vasculitis or giant cell arteritis, are advised this test.
- It is also useful in monitoring the efficacy of treatment in inflammatory conditions as well as lymphoma and TB.
- An ESR test is often conducted for the detection of bone infection.
- This test is also advised when myeloma is suspected.
This is a simple blood test that does not have any prior restrictions. Blood is drawn by a technician from the inside of the elbow.
Interpretation of results
The normal range is as follows:
For adults by the Westergren method:
- For men younger than 50 years old: below 15 mm/hr
- For men above 50 years old: below 20 mm/hr
- For women younger than 50 years old: below 20 mm/hr
- For women above 50 years old: below 30 mm/hr
For children (Westergren method):
- Newborns: 0 to 2 mm/hr
- Newborn to puberty: 3 to 13 mm/hr
The normal ranges for females are slightly higher than that of males. Besides this, ESR tends to increase with age. Obese people also have a slightly higher rate. It is customary to repeat the ESR test after some time if the results are elevated without any clinical symptoms as it is possible for sedimentation rate to be high even in the absence of disease. Factors that increase sedimentation rate are pregnancy, menstruation, anemia, malignancy, kidney disease in the last stage and any condition that increases fibrinogen.
Sedimentation rate above 100mm/hr is a definite indication of active infection that needs to be evaluated.
The sed rate is lower when the red blood cell count is high or when WBCs are notably high and in blood disorders like sickle cell anemia. Besides this, congestive heart failure, liver disease, hyperviscosity also reduces ESR.
Certain medicines, like, dextran, methyldopa, theophylline, and vitamin A tend to raise ESR, while cortisone, aspirin and quinine lower it.
Written by: Nandita tripati
Date last updated: January 10, 2015