Objective: The aim of this study was to evaluate the construct validity of a generic health related quality of life (HRQOL) instrument - the EQ-5D - in a sample of schizophrenic patients receiving antipsychotic treatment.
Research design and methods: A total of 2128 schizophrenic patients treated with olanzapine, 417 treated with risperidone, and 112 with haloperidol responded to the EQ-5D. The study also assessed the effect of patient age, gender, and co-morbidity variables on patient's HRQOL Main outcomes measures: EQ-5D scores at the start of treatment and after 3 and 6 months of therapy were compared with results from the Clinical Global Impression (CGI) severity of illness scale and the (GAF) scale. The effect of antipsychotics and sociodemographic variables on patient's HRQOL over time was tested through a three-factor doubly multivariate repeated measures MANCOVA.
Results: High scores in the GAF scale and low scores in the CGI were linked with high scores on the EQ-5D scale. The correlational effects observed between the EQ-5D and the clinical indices ranged from 0.33 to 0.54. A significant effect of 'visit time' as well as an interaction of 'visit time' x drug, 'visit time' x gender, and 'visit time' x co-morbidity was observed.
Conclusions: Results suggest the EQ-5D is a valid instrument capable of detecting HRQOL differences between schizophrenic patients with different degrees of severity of illness.