Objective: The purpose of this study was to clarify the process of establishing diagnostic criteria in epidemiological studies.

Methods: We interviewed a person with knowledge of the process of establishing diagnostic criteria for Kawasaki disease and subacute myelo-optico-neuropathy (SMON), and reviewed materials and literature.

Results: For Kawasaki disease, the diagnostic criteria were established by epidemiologists who developed a written guideline for the diagnosis while interviewing clinicians. Subsequently, the diagnostic criteria were revised according to the results of epidemiological studies. In SMON, the diagnostic criteria were mainly established by clinicians. The pathogenesis was subsequently recognized internationally, as a result of epidemiological studies. Although epidemiological studies are typically quantitative, qualitative processes played an important role in the first step, the establishment of diagnostic criteria.

Objective: The purpose of this study was to clarify the process of establishing diagnostic criteria in epidemiological studies.

Methods: We interviewed a person with knowledge of the process of establishing diagnostic criteria for Kawasaki disease and subacute myelo-optico-neuropathy (SMON), and reviewed materials and literature.

Results: For Kawasaki disease, the diagnostic criteria were established by epidemiologists who developed a written guideline for the diagnosis while interviewing clinicians. Subsequently, the diagnostic criteria were revised according to the results of epidemiological studies. In SMON, the diagnostic criteria were mainly established by clinicians. The pathogenesis was subsequently recognized internationally, as a result of epidemiological studies. Although epidemiological studies are typically quantitative, qualitative processes played an important role in the first step, the establishment of diagnostic criteria.