A novel methodological framework was described for detecting and quantifying overdiagnosis

•Quantification of overdiagnosis in noncancer contexts is critical to informing evidence-based decisions on the use of new (more sensitive) diagnostic tests and expanded disease definitions.•We describe a ‘Fair Umpire’ methodological framework which may be used to assess the presence of, and quantify the extent of, overdiagnosis of noncancerous conditions and demonstrate the framework using hypertension, gestational diabetes mellitus, and other examples.•This framework provides a method for deriving baseline estimates against which the effectiveness of interventions to prevent overdiagnosis could be measured.•The framework may also help health services to monitor new diagnostic processes, to detect potential overdiagnosis early.