Validity of self-reported hyperthyroidism and hypothyroidism: Comparison of self-reported questionnaire data with medical record review

Studies that aim at identifying genes or environmental factors contributing to the development of autoimmune thyroid disease (AITD) demand that severa l hundred patients and control subjects be assessed. In these large studies , the laboratory methodology is often described in detail whereas little at tention is given to an accurate description of the study population. Usuall y, a diagnosis of AITD in the control group is based on self-reported disea se status. Although such studies have been criticized for diagnostic inaccu racy, no study has evaluated the validity of self-reported hyperthyroidism and hypothyroidism in detail. We have assessed the validity of self-reporte d hyperthyroidism and hypothyroidism in 401 twin pairs from among 6,628 sam e gender pairs, ages 18-41 years who participated in a nationwide questionn aire survey in 1994. The self-reported questionnaire data were compared wit h information from medical records and the 1/kappa coefficient, sensitivity , and specificity were determined. Overall, there was only a slight to fair agreement between the self-reported questionnaire data and medical record data as shown by kappa values of 0.18, 0.21, and 0.26 for hyperthyroidism a nd hypothyroidism as a group, hyperthyroidism and hypothyroidism, respectiv ely. For both hyperthyroidism and hypothyroidism, the sensitivity of the se lf-reported diagnosis was 0.98, whereas the specificity was 0.57 and 0.67 f or self-reported hyperthyroidism and hypothyroidism, respectively. In concl usion, the validity of self-reported hyperthyroidism and hypothyroidism is unsatisfactorily low. However, by combining self-reports with valid retrosp ective data on diagnostic findings it can be used as a sampling method in l arge epidemiological or genetic studies.