Subjective quality of life (SQOL) is an established patient-reported outcome in the evaluation of treatments for psychosis. The use of SQOL measures in the presence of psychiatric symptoms and cognitive deficits has been questioned. However, there is little evidence on whether items function differently as indicators of SQOL in psychotic patients with different levels of symptoms and deficits. Substantial differential item functioning (DIF) would, indeed, challenge the validity of established measures. We aimed to investigate the validity of a widely used measure of subjective quality of life (SQOL), i.e., the Lancashire Quality of Life Profile (LQOLP), in the presence of cognitive deficits and psychiatric symptoms in patients with severe and enduring psychosis.
- Public Health, Environmental and Occupational Health