The emerging risk of overdiagnosis in rheumatoid arthritis and polymyalgia rheumatica.

Overdiagnosis occurs when patients are diagnosed with a disease that would otherwise never have affected the quality or duration of their lives. This often happens unintentionally through well-meaning screening programmes that aim to detect diseases during so-called subclinical stages. Recently, it has been suggested that patients with polymyalgia rheumatica should be screened for giant cell arteritis to identify those at higher risk of relapse or vascular complications. Screening for interstitial lung disease for patients with rheumatoid arthritis has also been recommended to identify patients who could benefit from pulmonary interventions. These potential benefits must be weighed against foreseeable harms. Such harms include the uncovering of incidental findings that necessitate additional medical follow-up, the financial costs associated with screening initiatives, the risk of overtreatment through increased immunosuppression in patients who might not have otherwise required it, and the psychosocial burden of a new diagnosis. Randomised clinical trials and prospective cohort studies of screening interventions should be conducted to establish the risks and benefits and identify patients most likely to benefit from them. This Viewpoint covers risks that overdiagnosis presents to the field of rheumatology, with focus on rheumatoid arthritis and polymyalgia rheumatica.