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

ObjectivesTo 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.MethodsA 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.ResultsGood internal consistency reliability was found for both the psychosocial and vitality domains (Cronbach's α = 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.ConclusionsThe 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.