A good history and detailed clinical examination of the patient are essential for a proper diagnosis of over 100 types of arthritis. Recognition of patterns of joint involvement (topography) and those of disease presentation and progression is essential for correct clinical diagnosis. In rheumatology practice, a working diagnosis can usually be made on proper examination of the patient. Laboratory tests, including X-Rays, are ordered later to confirm the diagnosis, rule out other possible causes, estimate the level of disease activity, or monitor drug toxicity. As with any other investigations, these must be obtained from a reliable laboratory. The results should always be interpreted in view of the clinical picture. These tests are expensive and must not be used indiscriminately. Laboratory studies are helpful in arthritis only if ordered in an appropriate clinical situation and interpreted accordingly. Measurement errors, laboratory variations due to various factors, and inherent limitations must always be born in mind. A positive test in the absence of an appropriate clinical setting can generally be overlooked.
Commonly used laboratory investigations are discussed below: