The Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) questionnaire. A validation study with Spanish schizophrenia spectrum outpatients

Abstract

Introduction. The Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) is a disease-specific subjective Quality of Life (QL) questionnaire for patients with schizophrenia. This study assesses the psychometric properties of the SQLS-R4 when applied to a sample of Spanish schizophrenia spectrum outpatients with stable disease.

Methods. The SQLS-R4 and EUROQOL-5D-5L were completed once by 168 schizophrenia and schizoaffective disorder patients. Of these, 61 also completed the WHOQOL-BREF and 50 completed the SQLS-R4 one week later. Psychometric evaluation of structure, reliability and validity was conducted.

Results. Multi-trait scaling confirmed the two multiitem scales. Internal consistency for the two scales (Cronbach’s coefficients>0.89) and the whole questionnaire (0.96) was adequate, as was test–retest reliability (intraclass correlation coefficients>0.79). Correlations with related areas of EUROQOL-5D-5L and WHOQOL-BREF (Spearman’s Rho>0.60) supported convergent validity. Divergent validity was confirmed through low correlations with less-related areas of these two questionnaires (Spearman’s Rho<0.30). Patients with higher levels of depression, more acute episodes and schizoaffective disorder had higher QL limitations.

Conclusions. The SQLS-R4 is a reliable and valid instrument when applied to Spanish outpatients with stable disease. The results of our validation study concur with those of other psychometric studies performed in Europe and other cultural areas.