How far do alternative capability and health-related quality of life instruments capture differing aspects of mental wellbeing for schizophrenic patients with depression?

Abstract BackgroundThere is increasing evidence that assessing outcomes in terms of capability provides information beyond that of health-related quality of life (HRQoL) for evaluation of outcomes in mental health research and clinical practice. Aims This paper aimed to assess similarities and differences in the measurement properties of the ICECAP-A and OxCAP-MH instruments in schizophrenic patients with depression, and compare these measurement properties to those of (i) EQ-5D-5L / EQ VAS instruments and (ii) mental health specific measures.Method Using data for 100 patients from the UK, measurement properties were compared using correlation analyses, Bland Altman plots and exploratory factor analysis (EFA). Responsiveness was assessed by defining groups who worsened, improved or remained unchanged, based on whether a clinically meaningful change in the instrument scores between baseline and 9-month follow-up assessments. ResultsThe two capability instruments had stronger convergent validity with each other (0.677) than with the HRQoL (0.354-0.431) or the mental health specific (0.481-0.718) instruments. The OxCAP-MH tended to have stronger correlations with mental health specific instruments than the ICECAP-A, while the ICECAP-A had slightly stronger correlation with the EQ VAS. Change scores of the capability instruments weakly correlated with change scores of the health-related HRQoL scales (0.131-0.269), but moderately with those of mental health specific instruments for the ICECAP-A (0.355-0.451) and moderately/strongly for the OxCAP-MH (0.437-0.557). ConclusionsAssessing outcomes in terms of capabilities for schizophrenic patients with depression provided more relevant, mental health specific information than the EQ-5D-5L or the EQ VAS. The ICECAP-A and the OxCAP-MH demonstrated similar psychometric properties, but the OxCAP-MH was more correlated with disease-specific instruments.