Quality of life measurement in schizophrenia: reconciling the quest for subjectivity with the question of reliability

Background. The patients' ability to appriase their quality of life in schizophrenia was studied by examining the reliability and the validity of self-rated quality of life estimates. Methods. Sixty-three symptomatically stable patients with schizophrenia (DSM-IV) receiving maintenance treatment were evaluated over a 4-week period. The subjects were asked to appraise their quality of life at weekly intervals on a single item global quality of life measure, as well as the self-administered sickness impact profile. The patients' quality of life was also rated by a clinician using the social performance schedule and the global assessment scale of functioning; and clinical aspects such as the severity of psychotic symptoms, neurocognitive deficits, dose of medications, and side effects were documented with standardized measures. Results. The results indicated that the patients' self-reports were highly consistent over the 4 weeks, and the quality of life ratings correlated significantly with the clinician's estimates. The patients' quality of life was predictably influenced by the severity of their symptoms, side effects, cognitive deficits and the dose of their antipsychotic medication, but the reliability of their reports was not materially affected by these factors. Conclusions. It is concluded that clinically compliant and stable patients with schizophrenia can evaluate and report their quality of life with a high degree of reliability and concurrent validity, implying that self-report measures are potentially useful tools in clinical trials and outcome studies.