Valid sarcoidosis incidence assessment is contingent on access to medical care, thoroughness of reportage, assiduity of radiographic interpretation, employment and health care screening policies, misclassification, and population ethnicity. To diminish ambiguity and foster inter-population comparison, the term "sarcoidosis incidence" must be modified to convey the methodology employed in compiling the numerator. In age-delimited cohorts, valid comparison to population incidence requires age adjustment due to the age-dependency of incidence. The "true incidence" of sarcoidosis is a notional concept: more than 90% of cases are subclinical and radiographically inevident. Occupational causal inference based on incidence differential vs. populations has been undermined by methodological differences in ascertainment and computation.
Keywords: Diagnosis; Epidemiology; Etiology; Radiography; Sarcoidosis; Statistics and Numerical data.