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

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 (rs 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 (rs 0.44) and a large correlation between the SQLS-R4 “psychosocial” domain and the EuroQol five-dimensional questionnaire “anxiety/depression” domain (rs 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.