Laboratory tests for rheumatic diseases. When are they useful?

Because negative tests often do not exclude a rheumatic disease and positive tests do not always diagnose it, judicious use of laboratory testing in patients with suspected rheumatic disease is essential. The final diagnosis must be made clinically. However, when the tests are used in conjunction with clinical manifestations, they may help differentiate the numerous rheumatic disorders, and they may also be of value in monitoring activity of the disease.