Caregiving in schizophrenia: development, internal consistency and reliability of the Involvement Evaluation Questionnaire--European Version. EPSILON Study 4. European Psychiatric Services: Inputs Linked to Outcome Domains and Needs

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. Declaration of interest: No conflict of interest. Funding detailed in Acknowledgements.