Quality of Life Assessment in schizophrenia - development of a short version of the QLiS

Abstract

The QLiS (Quality of Life in Schizophrenia) is a disease-specific questionnaire with high content validity and sound psychometric properties. It comprises 54 items related to 12 subscales. However, its use in surveys or clinical studies is limited due to its length. Our aim was to develop and validate a short form of the QLiS.

Four steps were taken to develop the short form (QLiS-SF) using samples from the Clinical Analysis of the Treatment of Schizophrenia study. 1. A model with second order scales was developed using exploratory factor analysis. 2. The resulting model was tested in an independent sample using confirmative factor analysis (CFA). 3. Based on this model, items were selected on grounds of distributional properties, content reviews, and item loadings. 4. The resulting short form was validated independently through CFA.

Results

Three second order scales were constructed: illness-related quality of life, social life, and global subjective well-being. CFA of the new theoretical model resulted in a CFI of 0.67 and absolute fit indices of CMIN/df = 2.55, RMSEA = 0.08, SRMR = 0.09. We selected 13 items that showed good statistical properties and good fit of content to subscale. Fit of the underlying theoretical model with the 13 items was satisfactory (CFI = 0.95, CMIN/df = 2.23, RMSEA = 0.06, SRMR = 0.04). Composite reliability scores for the three subscales were above 0.70.

The QLiS-SF showed adequate model fit and reliability. It offers a novel, well-founded opportunity to assess quality of life in persons with schizophrenia in situations in which the application of the long version is not considered possible.

Disclosure of interest

The authors have not supplied their declaration of competing interest.