| SUSAN LECLAIR |
First - an
acknowledgement - this is NOT my favorite test. Many laboratorians
believe that physicians use it too often and inappropriately.
ESR stands for erythrocyte sedimentation rate or sed rate. There are
three different methods used here; one of which is Westergren. Each of
the three has different reference values and cannot be interchanged with
each other.
Red cells settle through plasma because they weigh more than the plasma.
But plasma's weight can vary as different proteins become more or less
concentrated in the fluid. Proteins such as inflammatory proteins are
lighter in weight than antibodies for example so red cells will drop
"faster" through plasma containing the inflammatory proteins than they
would if there were a lot of antibodies in the plasma. Because of this,
ESR tend to be elevated in situations in which there are lots of
inflammatory proteins - conditions such as rheumatoid arthritis,
colitis, Crohn's disease, fibromalagia. ESR's will also be elevated if
the red cells are larger than they should be or if the patient is anemia
and there are less red cells than there should be.
ESR's are NOT an accurate test of any diagnosis. It should be used only
in situations of chronic inflammation and the results should be compared
not to a reference but to the patient's last ESR. If, for example, the
ESR seems to be going up, then you know that inflammation is continuing
and getting worse, If, on the other hand, the ESR is going down, then
you know that inflammation is lessening.
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