Measurement limit of quality-of-life questionnaires in psychiatric settings.
OBJECTIVE
The extent to which psychiatric patients with a broad spectrum of disability can validly self-report on their quality of life (QOL) remains unknown. Therefore, the aim of this study was to clarify the measurement limit of a QOL questionnaire in psychiatric settings.


METHODS
We examined this issue by assessing data quality, reliability, and validity of the MOS 36-Item Short-Form Health Survey (SF-36) in 137 chronically mentally ill inpatients. We also attempted to identify the impact of cognitive impairment on the validity of the SF-36 and ascertain the points throughout the continuum of cognitive functioning at which self-reported data become compromised.


RESULTS
Cognitive functioning was a major determinant of the data quality, and the psychometric properties of this instrument were marginally acceptable only in patients with Mini-Mental State Examination scores of 28 or higher.


CONCLUSIONS
Measuring QOL reliably and validly through self-report may be possible in psychiatric patients with only very slight cognitive impairment. Therefore, interviewer-administered instruments that measure QOL may be preferable to questionnaires in psychiatric settings.
Nishiyama
Takeshi
T
Clinical Trial Management Center, Nagoya City University Hospital, Mizuho-ku, Nagoya, Japan. nishiyama@minos.ocn.ne.jp
Ozaki
Norio
N
D000328:Adult; D004185:Disability Evaluation; D005260:Female; D006778:Hospitals, Psychiatric; D006801:Humans; D007297:Inpatients / Q000523:psychology*; D007564:Japan; D008297:Male; D001523:Mental Disorders / Q000523:psychology* / Q000534:rehabilitation; D008875:Middle Aged; D010555:Personality Inventory / Q000706:statistics & numerical data; D011594:Psychometrics; D011788:Quality of Life / Q000523:psychology*; D012649:Self Concept; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires