overdiagnosis

Overdiagnosis is the diagnosis of a medical condition that would not have caused symptoms or death during a patient’s lifetime. It frequently arises through screening programs, advanced imaging, and broadened disease definitions. While early detection may improve outcomes for some individuals, overdiagnosis can lead to unnecessary treatment and anxiety for others. It is distinct from false positives or misdiagnosis, in that the condition is real but its natural course would have remained inconsequential.

Causes and mechanisms include screening with high sensitivity that detects indolent lesions, lead-time and length-time bias, incidental findings, and expanding diagnostic criteria. Conditions with variable natural history, such as slow-growing cancers or preclinical disease states, are particularly prone. Distinguishing overdiagnosed cases from those that would progress remains challenging.

Consequences include overtreatment with surgery, radiation, or systemic therapy; adverse effects; psychological burden; increased healthcare costs; and resource diversion. It can also influence prognosis estimates and policy decisions.

Examples include prostate cancer detected by PSA screening, which may not progress; DCIS of the breast detected by mammography; thyroid cancers found incidentally on imaging; cervical intraepithelial lesions in routine screening where some would regress; and increasingly detected nodules in lung cancer screening programs.

Approaches to reduce overdiagnosis emphasize shared decision-making, risk-based or age-stratified screening, and the use of active surveillance for low-risk lesions. Researchers use statistical methods to estimate excess incidence and model harms and benefits. Clear communication about the uncertainty and likely natural history is essential.