MadSci Network: Medicine

Re: What is ESR and what are normal levels of it found in our blood?

Date: Sat Sep 25 10:00:13 1999
Posted By: Sean Moore, M.D., emergency medicine, smbd jewish general hospital
Area of science: Medicine
ID: 936297024.Me

     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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