Cross validation of a general population survey diagnostic interview: a comparison of CIS-R with SCAN ICD-10 diagnostic categories

Background. Comparisons of structured diagnostic interviews with clinical assessments in general population samples show marked discrepancies. In order to validate the CIS-R, a fully structured diagnostic interview used for the National Survey of Psychiatric Morbidity in Great Britain, it was compared with SCAN, a standard, semi-structured, clinical assessment. Methods. A random sample of 1882 Leicestershire addresses from the Postcode Address File yielded 1157 eligible adults. of these 860 completed the CIS-R; 387 adults scores greater than or equal to 8 on the CIS-R and 205 of these completed a SCAN reference examination. Neurotic symptoms, in the previous week and month only, were enquired about. Concordance was estimated for ICD-10 neurotic and depressive disorders, F32 to F42 and for depression symptom score. Results. Sociodemographic characteristics closely resembled National Survey and 1991 census profiles. Concordance was poor for any ICD-10 neurotic disorder (kappa = 0.25 (95% CI, 0.1-0.4)) and for depressive disorder (kappa = 0.23 (95% CI, 0-0.46)). Sensitivity to the SCAN reference classification was also poor. Specificity ranged from 0.8 to 0.9. Rank order correlation for total depression symptoms was 0.43 (Kendall's tau b; P < 0.001; N = 205). Discussion. High specificity indicates that the CIS-R and SCAN agree that prevalence rates for specific disorders are low compared with estimates in some community surveys. We have revealed substantial discrepancies in case finding. Therefore, published data on service utilization designed to estimate unmet need in populations requires re-interpretation. The value of large-scale CIS-R survey data can be enhanced considerably by the incorporation of concurrent semi-structured clinical assessments.