Laboratory tests in rheumatic diseases: a guide for clinicians

Abstract

In the practice of rheumatology, just as in other disciplines of medicine, laboratory tests are meant to supplement a thorough history and physical examination. The clinician should have a purpose for ordering each test; to screen for a disorder, confirm a diagnosis, exclude a possible diagnosis, monitor therapy or determine prognosis. Many of the rheumatic diseases have in common processes and features that are inflammatory and many of the tests merely establish the presence of an inflammatory process. The measurement of ESR and C-reactive protein are two such tests most widely used. The systemic rheumatic diseases also manifest serologically with the continual production of non-organ specific autoantibodies. Few of these antibodies are specific for a particular disease. The majority of the autoantibodies are positive in various disease states and are only useful as adjuncts to the diagnosis of rheumatic diseases. This discussion deals with commonly ordered tests in rheumatic diseases; how to use the tests appropriately while keeping in mind their limitations.