A Primer on Rheumatologic Laboratory Tests: What They Mean and When to Order Them.

Rheumatologic laboratory tests are frequently ordered by primary care physicians in patients who complain of joint pain. Clinicians should keep in mind the pretest probability of a rheumatologic disorder before ordering any test because laboratory tests in rheumatology are not diagnostic of any particular disease. Any rheumatologic laboratory test result should only be used to further refine the diagnosis, and it should not replace a thorough history and physical examination. In this article, the authors discuss the diagnostic utility of the commonly ordered rheumatologic laboratory tests based on their sensitivity, specificity, and likelihood ratios.