CRP and Sedrate - What"s the Difference Between the Two Blood Tests?
Updated July 28, 2015.
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. Are sedrate and CRP results specifically significant to a certain type of arthritis? Are the two blood tests elevated in all inflammatory conditions?
Answer:
Sedrate 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 sedrate and CRP measure the increase in inflammatory generated proteins.
- CRP is a direct measurement of C-reactive protein.
- Sedrate 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, an inflammatory type of arthritis, there are cases where both the sedrate 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 sedrate 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?
The Bottom Line
While diagnosis is not dependent on results of either sedrate or CRP, they are commonly ordered tests. If they are elevated, it helps to confirm that an inflammatory process exists. Learn more about each test:
Sources:
Clinical Diagnosis by Laboratory Methods. Todd-Sanford. 15th Edition.
Primer on the Rheumatic Diseases. Arthritis Foundation. Thirteenth edition.
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