Factor structure of the Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4)

Abstract

The Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4) appears to offer excellent potential as an easily administered and patient acceptable assessment and monitoring measure of quality of life (QoL). However, a principle psychometric criterion crucial to the use and validity of the instrument concerns the underlying factor structure. The SQLS-R4 comprises two sub-scales, these being cognition and vitality QoL and psychosocial feelings QoL. However, the factor structure of the SQLS-R4 has yet to be established in a patient group in the UK. Confirmatory factor analysis was conducted on the SQLS-R4 to determine its psychometric properties in 100 patients with a primary ICD-10 diagnosis of schizophrenia. Internal reliability of the SQLS-R4 cognition and vitality QoL and psychosocial feelings QoL sub-scales was found to be excellent. Consistent with the original validation of the SQLS-R4, two correlated factors comprising cognition and vitality QoL and psychosocial feelings QoL were observed to offer the best fit to the data. In conclusion, the SQLS-R4 would appear to be suitable for use in patients with a primary diagnosis of schizophrenia in the UK. Potential clinical uses and the direction of future research with the SQLS-R4 are indicated.

Keywords:

• Factor analysis
• psychometrics
• quality of life
• schizophrenia
• SQLS

Acknowledgements

We are grateful to all the patients who took part in the study and to our clinical colleagues for assistance and support. We are also indebted to Diane Wild at Oxford Outcomes Ltd. for permission to use the SQLS-R4 in our research.

Notes

1. All statistical analyses reported are two-tailed and alpha is set at p = .05 unless otherwise indicated.

2. Observed power was low for the ANOVAs. Type 2 error is consequently a possibility in these analyses.