Validation of the Schizophrenia Quality of Life Scale Revision 4 among Chronic Schizophrenia Patients in Malaysia

Abstract

Objectives: To explore the validity and reliability of a disease-specific health-related quality-of-life questionnaire-the Schizophrenia Quality of Life Scale Revision 4 (SQLS-R4)-in patients with schizophrenia in Malaysia. Methods:A total of 222 outpatients with schizophrenia receiving treatment at the Universiti Kebangsaan Malaysia Medical Centre completed the SQLS-R4 in either the Malay or the English language. A generic self-report health-related quality-of-life measure-the EuroQoL group EuroQol five-dimensional questionnaire-and a measure of symptom severity-the Clinical Global Impression-Schizophrenia scale-were also administered to assess validity. Results: Good internal consistency reliability was found for both the psychosocial and vitality domains (Cronbach's ? = 0.95 and 0.85, respectively). Most items were also significantly correlated with their own scale score (r s ranging from 0.29 to 0.74). There was a moderate correlation between the SQLS-R4 "vitality" domain and the EuroQol five-dimensional questionnaire "usual activities" domain (r s = 0.44) and a large correlation between the SQLS-R4 "psychosocial" domain and the EuroQol five-dimensional questionnaire "anxiety/depression" domain (r s = 0.44-0.57). Most of the symptom dimensions of the Clinical Global Impression-Schizophrenia scale were also moderately correlated with the SQLS-R4 subscale scores. Conclusions:The SQLS-R4 is a valid and reliable health-related quality-of-life instrument for use in minimally ill patients with schizophrenia in Malaysia, but some of the items may be redundant and irrelevant. Validation of SQLS-R4 in different types of patients and various levels of illness severity is required to further verify its application.