Abstract
Objective
To assess the psychometric properties of the Schizophrenia Quality of Life Scale (SQLS) in Asians with schizophrenia in Singapore.
Methods
A consecutive sample of outpatients with schizophrenia completed the English or Chinese version of the SQLS and the Short-Form 36 Health Survey (SF-36) twice during two different clinic visits. The patients were also assessed for presence or absence of 22 psychiatric symptoms.
Results
About 202 patients (English-speaking: 140) participated in the study. Correlations between SQLS scales and other measures assessing similar constructs ranged from 0.46 to 0.69 (P < 0.001 for all). For SQLS psychosocial and symptoms/side effects scales, item-to-scale correlations were >0.4, Cronbach’s alpha and intra-class correlation coefficient values were close to or exceed 0.7, and Cohen’s effect size, standardized response mean, and Guyatt’s responsiveness index values approximated or exceeded 0.2 for both SQLS language versions; however, for the energy/motivation scale, item-to-scale correlations (range: 0.08–0.51), reliability (range: 0.46–0.66) and responsiveness (range: 0.04–0.08) statistics were not satisfactory for both SQLS versions.
Conclusions
The SQLS psychosocial and symptoms/side effects scales are valid, reliable and responsive in Singaporean patients with schizophrenia; the appropriateness of energy/motivation scale requires further investigation.
Similar content being viewed by others
References
Saha, S., Chant, D., Welham, J., & McGrath, J. (2005). A systematic review of the prevalence of schizophrenia. PLoS Medicine, 2, e141.
Pinikahana, J., Happell, B., Hope, J., & Keks, N. A. (2002). Quality of life in schizophrenia: A review of the literature from 1995 to 2000. International Journal of Mental Health Nursing, 11, 103–111.
Bobes, J., Garcia-Portilla, P., Saiz, P. A., Bascaran, T., & Bousono, M. (2005). Quality of life measures in schizophrenia. European Psychiatry, 20(Suppl 3), 313–317.
Hewitt, J. (2007). Critical evaluation of the use of research tools in evaluating quality of life for people with schizophrenia. International Journal of Mental Health Nursing, 16, 2–14.
Katschnig, H. (2000). Schizophrenia and quality of life. Acta Psychiatrica Scandinavica, 102, 33–37.
Guyatt, G. H., Jaeschke, R., Feeny, D. H., & Patrick, D. L. (1996). Measurement in clinical trials: Choosing the right approach. In Spilker B. (Ed.), Quality of life and pharmacoeconomics in clinical trials (pp. 41–48). Philadelphia: Lippincott-Raven Publishers.
Osoba, D. (1998). Guidelines for measuring health-related quality of life in clinical trials. In Staquet M. J., Hays R. D., & Fayers P. M. (Eds.), Quality of life assessment in clinical trials methods and practice (pp. 19–35). Oxford: Oxford University Press.
Awad, A. G. (1992). Quality of life of schizophrenic patients on medications and implications for new drug trials. Hospital & Community Psychiatry, 43, 262–265.
Heinrichs, D. W., Hanlon, T. E., & Carpenter, W. T. Jr. (1984). The Quality of Life Scale: An instrument for rating the schizophrenic deficit syndrome. Schizophrenia Bulletin, 10, 388–398.
Skantze, K., Malm, U., Dencker, S. J., May, P. R., & Corrigan, P. (1992). Comparison of quality of life with standard of living in schizophrenic out-patients. British Journal of Psychiatry, 161, 797–801.
Oliver, J., Huxley, P., Bridges, K., & Kaiser, W. (1996). Quality of life and mental health services. London: Routledge.
Lehman, A. F., Ward, N. C., & Linn, L. S. (1982). Chronic mental patients: The quality of life issue. American Journal of Psychiatry, 139, 1271–1276.
Wilkinson, G., Hesdon, B., Wild, D., Cookson, R., Farina, C., & Sharma, V., et al. (2000). Self-report quality of life measure for people with schizophrenia: The SQLS. British Journal of Psychiatry, 177, 42–46.
Kaneda, Y., Imakura, A., Fujii, A., & Ohmori, T. (2002). Schizophrenia Quality of Life Scale: Validation of the Japanese version. Psychiatry Research, 113, 107–113.
Guillemin, F., Bombardier, C., & Beaton, D. (1993). Cross-cultural adaptation of health-related quality of life measures: Literature review and proposed guidelines. Journal of Clinical Epidemiology, 46, 1417–1432.
Ware, J. E., Snow, K. K., Kosinski, M., & Gandek, B. (1993). SF-36 health survey manual and interpretation guide. New York: New England Medical Center.
Ware, J. E., Kosinski, M., & Dewey, J. E. (2000). How to score version 2 of the SF-36 Health Survey. Lincoln: QualityMetric Inc.
Thumboo, J., Fong, K. Y., Machin, D., Chan, S. P., Leong, K. H., & Feng, P. H., et al. (2001). A community-based study of scaling assumptions and construct validity of the English (UK) and Chinese (HK) SF-36 in Singapore. Quality of Life Research, 10, 175–188.
Wilkinson, G., Wild, D., Fitzpatrick, R., Jenkinson, C., & Hesdon, B. (1999). User manual for the SQLS. Headington: Oxford Outcomes.
Browne, S., Roe, M., Lane, A., Gervin, M., Morris, M., & Kinsella, A., et al. (1996). Quality of life in schizophrenia: Relationship to sociodemographic factors, symptomatology and tardive dyskinesia. Acta Psychiatrica Scandinavica, 94, 118–124.
Meltzer, H. Y., Burnett, S., Bastani, B., & Ramirez, L. F. (1990). Effects of six months of clozapine treatment on the quality of life of chronic schizophrenic patients. Hospital & Community Psychiatry, 41, 892–897.
Juniper, E. F., Gordon, H. G., & Roman, J. (1996). How to develop and validate a new health-related quality of life instrument. In Spilker B. (Ed.), Quality of life and pharmacoeconomics in clinical trials (pp. 49–56). Philadelphia: Lippincott-Raven Publishers.
Fayers, P. M., & Machin, D. (2000). Quality of life: Assessment, analysis and interpretation. Chichester: John Wiley & Sons.
Hays, R. D., Anderson, R. T., & Revicki, D. (1998). Assessing reliability and validity of measurement in clinical trials. In Staquet M. J., Hays R. D., & Fayers P. M. (Eds.), Quality of Life assessssment in clinical trials methods and practice (pp. 169–182). Oxford: Oxford University Press.
Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Hillsdale: Lawrence Earlbaum Associates.
Deyo, R. A., Diehr, P., & Patrick, D. L. (1991). Reproducibility and responsiveness of health status measures. Statistics and strategies for evaluation. Controlled Clinical Trials, 12, 142S–158S.
Guyatt, G., Walter, S., & Norman, G. (1987). Measuring change over time: Assessing the usefulness of evaluative instruments. Journal of Chronic Diseases, 40, 171–178.
Schunemann, H. J., & Guyatt, G. H. (2005). Commentary—goodbye M(C)ID! Hello MID, where do you come from? Health Services Research, 40, 593–597.
Kay, S. R., Fiszbein, A., & Opler, L. A. (1987). The positive and negative syndrome scale (PANSS) for schizophrenia. Schizophrenia Bulletin, 13, 261–276.
Overall, J. E., & Gorham, D. R. (1962). The brief psychiatric rating scale. Psychological Reports, 10, 799–812.
Peto, V., Jenkinson, C., & Fitzpatrick, R. (2001). Determining minimally important differences for the PDQ-39 Parkinson’s disease questionnaire. Age Ageing, 30, 299–302.
Walters, S. J., & Brazier, J. E. (2003). What is the relationship between the minimally important difference and health state utility values? The case of the SF-6D. Health Quality of Life and Outcomes, 1, 4.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Luo, N., Seng, BK., Xie, F. et al. Psychometric evaluation of the Schizophrenia Quality of Life Scale (SQLS) in English- and Chinese-speaking Asians in Singapore. Qual Life Res 17, 115–122 (2008). https://doi.org/10.1007/s11136-007-9278-1
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11136-007-9278-1