Validity of a common quality of life measurement in homeless individuals with bipolar disorder and schizophrenia

Abstract

Objective: To provide new evidence regarding the validity, reliability, sensitivity to change and acceptability of a schizophrenia (SCZ) quality of life measurement (S-QoL 18) in homeless people with bipolar disorder (BPD).

Methods: This multi-centre prospective study was conducted in the following 4 French cities: Lille, Marseille, Paris and Toulouse. In addition to the S-QoL 18, data on sociodemographic information, disease severity using the Modified Colorado Symptom Index (MCSI), recovery using the Recovery Assessment Scale (RAS) and QoL using the Short-Form Health Survey (SF-36) were collected. The S-QoL 18 was tested for construct validity, reliability, external validity, sensitivity to change and acceptability.

Results: In total, 216 homeless patients with BPD participated in this study. The eight-factor structure of the S-QoL 18 was confirmed by confirmatory factor analysis (RMSEA=0.058, CFI=0.98, TLI=0.966). The scalability was satisfactory, with INFIT statistics within an acceptable range (from 0.77 to 1.20). The internal consistency (from 0.43 to 0.76) and reliability coefficients (Cronbach's alpha from 0.65 to 0.86) were satisfactory for all dimensions. The external validity testing revealed that the S-QoL 18 dimension scores were significantly correlated with the MCSI, the RAS and the SF-36 scores. The percentage of missing data for the dimensions (<15%) and sensitivity to change were satisfactory.

Conclusions: These results demonstrate adequate acceptability and psychometric properties of the S-QoL 18 among homeless patients with BPD. The S-QoL 18 can be a common instrument for measuring QoL in homeless people with SCZ and BD.

Keywords: Bipolar disorder; Homeless; Outcome assessment; Psychometric properties; Quality of life.