|MadSci Network: Medicine|
The ESR is a test which takes a standard tube of whole blood, and measures the amount of red blood cells (RBCs) which collect at the bottom of the tube over a one hour period. It actually measures the clear zone above the RBCs. Increases in the test score will often reflect increases of proteins in the blood. This can be due to many different causes, including infections, pregnancy, obesity, cancers, collagen vascular diseases, and kidney failure. However, the test cannot be used to tell what is going on in the body. It can be used to help show that an inflammatory condition exists when there is insufficient other evidence, or as a means to follow the course of a disease. There are some major problems with the test: 1. It can be normal in very sick patients 2. It doesn't help find out what is wrong 3. It is difficult to do technically Specifically, in the case which you describe, it is important to know that most types of anemia falsely increase the ESR. There are two methods of measuring the ESR, called the Westergren and Wintrobe methods. The Westergren method is better in cases of anemia, and there is a formula to roughly correct for the amount of anemia (Corrected ESR = ESR ;ms [(Std. Ht - Actual Ht) × 1.75], where Std. Ht (standard hematocrit) is 45 for males and 42 for females. The ESR is also generally higher in older people. Some people use a formula to calculate normal ESR with age: for men, age in years ÷ 2; for women, (age in years + 10) ÷ 2. So it looks like you should look a bit further before deciding if the problem is the test or something else. I hope that this is helpful. Source: Ravel. Clinical Laboratory Medicine, 6th ed., Copyright © 1995 Mosby-Year Book, Inc.
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