Quality of Life Scale (QLS): A systematic review of measurement properties.

BACKGROUND AND HYPOTHESIS: Schizophrenia profoundly affects the quality of life of individuals living with the disorder. Despite the availability of numerous measurement tools, there is no consensus which one should be used as standard. As a first step, systematic reviews about the measurement properties of the various scales are needed, but such reviews are not available. STUDY DESIGN: We provide a systematic review of the Clinician-Rated Outcome Measure (ClinROM) Quality of Life Scale (QLS). We evaluated its measurement properties using the COnsensus-based Standards for the selection of health Measurement INstrument (COSMIN) guidelines. STUDY RESULTS: Of 4331 papers identified by a search in PubMed and EMBASE, 15 met the inclusion criteria. The QLS demonstrated good inter-rater reliability, known-groups validity and convergent validity of certain subscales. However, major limitations were identified in its development and content validity, and both evidence for structural validity and convergent validity of total scores. Internal consistency could not be conclusively evaluated due to insufficient structural validity. CONCLUSION: Given its substantial limitations, the QLS has been classified in COSMIN's recommendation category C. Following COSMIN's criteria, its use cannot be generally recommended.