Caregiving in schizophrenia: development, internal consistency and reliability of the Involvement Evaluation Questionnaire – European Version

Background In international research on the consequences of psychiatric illnesses for relatives of patients, the need for an internationally standardised measure has been identified. Aims To test the internal consistency and the test-retest reliability of the Involvement Evaluation Questionnaire (IEQ) in five European countries. Method The IEQ was administered twice to a sample of relatives or friends of patients with an ICD-10 diagnosis of schizophrenia. Reliability was tested using Cronbach's α , intraclass correlation coefficients and standard error of measurement. Reliability estimates were tested between sites. Results Test sample sizes ranged from 30 to 90 across sites, and retest sample sizes ranged from 21 to 77. Cronbach's α values of IEQ sub-scales and sumscore were substantial at most sites; but at two, α values were moderate. Intraclass correlation coefficients were substantial to high at all sites. The standard errors of measurement differed across sites, indicating differences in performance. Conclusion The reliability of the IEQ in five languages varies across sites, but is sufficiently high in at least four out of five.