Rheumatic disorders in a health survey: how valid and reliable are the reports?

The validity and reliability of interview reports on rheumatic disorders in a Swedish nationwide health survey were studied. Two samples, including altogether 157 individuals, who had reported rheumatic disorders, were medically examined 6 to 24 months after the original interview. The reproducibility of the original interview was studied by the means of two re-interviews. The proportional distribution of rheumatic disorders according to diagnostic group was similar to that in the original interview, in the two re-interviews and at the medical examination. In a subject-to-subject comparison the overall agreement between the medical examination and the lay re-interview was 84% (kappa 0.35) regarding presence of rheumatic disorders, and 57% (kappa 0.41) regarding matching of rheumatic diagnostic groups. In the original interview and the lay re-interview the same individual rheumatic disorder was reported by 38% of the subjects; 58% agreed regarding rheumatic diagnostic groups. The interview reports on rheumatic disorders in the health survey can therefore be considered to have acceptable validity and reliability only with regard to the proportional distribution of groups of rheumatic disorders, based on aggregated data.