Validity of the Composite International Diagnostic Interview (CIDI) psychosis module in a psychiatric setting

This study aimed to test the procedural validity of the psychosis module of the Composite International Diagnostic Interview (CIDI) by comparing it with diagnostic checklists completed by experienced clinicians. Seventy-five subjects were interviewed using the interviewer-administered version of the CIDI. Their clinician(s) then completed diagnostic checklists for DSMIV and ICD10 diagnoses of schizophrenia. Agreement was measured at the diagnostic, criterion and subcriterion levels. The validity standard (diagnostic checklist) was shown to be reliable with interrater agreement between the clinicians for the diagnosis of schizophrenia being excellent (kappa = 0.82 for DSMIV and kappa = 0.71 for ICD10). The agreement between the CIDI and the clinician checklists varied with sensitivities for DSMIV subcriteria ranging from 0.18 (negative symptoms) to 0.93 (bizarre delusions) and specificities ranging from 0.38 (catatonia) to 0.95 (disorganised speech). A similar pattern was found for ICD10 subcriteria: sensitivity varied from 0.19 (neologisms) to 0.90 (persistent delusions) and specificity varied from 0.39 (catatonia) to 0.95 (negative symptoms). The poorest levels of agreement were found for symptoms requiring interviewer judgement. The CIDI showed good agreement with clinician checklist diagnoses when the criteria were based on questions asked of the subjects. When the interviewer was required to make judgement of behaviours, the agreement between the CIDI and the clinician checklists was lower, resulting in overall poor agreement between the CIDI and the clinician checklists. Suggestions for improving the validity of the psychosis module of the CIDI are made.