CRP (C-reactive protein) / ESR (erythrocyte sedimentation rate)
Erythrocyte sedimentation rate or sedrate (ESR) and C-reactive protein (CRP) are commonly ordered tests for arthritis. During the acute phase response to a local or systemic inflammatory process, plasma proteins dramatically increase. C-reactive protein is one of the major plasma proteins generated, and is easily measured by laboratory testing.
Measures of inflammation
In general both ESR and CRP measure the increase in inflammatory generated proteins.
There are subtle differences in the behavior of the tests, depending on the suspected disease.
Are these tests specific for a certain disease? Are they always necessarily elevated in all inflammatory conditions?
The answer is no to both questions.
For example:
In rheumatoid arthritis which is a known inflammatory type of arthritis, there are cases where both the ESR and CRP are normal, particularly during the earliest stages of the disease. In certain patients, the reason for this appears to be an insensitivity or low level of a triggering mechanism that normally stimulates the liver to produce the inflammatory proteins necessary for ESR and CRP testing.
The diagnosis of rheumatoid arthritis, therefore, is not dependent on the presence of either test.
Related Resources - CRP (C-reactive protein) - ESR (erythrocyte sedimentation rate)
(Answer provided by the late Dr. Raymond Federman, aka Dr. Bones, who passed away on September 2, 2003. The care of his patients even in retirement was always his joy.)
Last update 12/19/05
