Question: CRP and Sedrate - What's the Difference?
ESR (erythrocyte sedimentation rate), also referred to simply as "sedrate", and CRP (C-reactive protein) are common blood tests often ordered when arthritis is being diagnosed or monitored. Is ESR and CRP specific to a certain type of arthritis? Is ESR and CRP elevated in all inflammatory conditions? What is the significance of the blood tests ESR and CRP?
Sedrate (ESR) and 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.
- CRP is a direct measurement of C-reactive protein.
- ESR indirectly measures many proteins associated with inflammation.
There are subtle differences in the behavior of the tests, depending on the suspected disease.
Are the Tests Disease-Specific?
The answer is no. For example: In rheumatoid arthritis, 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 result of either test.
- Do normal blood test results rule out rheumatic disease?
- What blood tests are commonly ordered to diagnose and monitor arthritis?
- Do blood tests monitor the effectiveness and toxicity of arthritis treatments?
Answer provided by rheumatologist Raymond Federman, M.D.