Common laboratory tests for rheumatological disorders: how do they help the diagnosis?

No screening test is ideal for detecting rheumatic diseases; diagnosis depends on appropriate history and thorough physical examination. Sometimes, laboratory investigations may be useful in confirming or ruling out rheumatic disease after a clinical diagnosis is considered. Once a rheumatic disease has been diagnosed, certain laboratory tests can help in assessing prognosis or determining the extent of the disease. Laboratory tests may also help the physician monitor certain rheumatic diseases, guide treatment or assess potential drug toxicity.