Evaluating the reliability and validity of SF-8 with a large representative sample of urban Chinese

Background: The Short Form-8 (SF-8) is a widely used instrument for measuring health-related quality of life (HRQOL). The purpose of the current study is to evaluate the reliability and validity of the Chinese version SF-8 using a large, representative sample of city residents in mainland China.

Methods: We surveyed residents of 35 major cities in China using random digit dialing of both landlines and cell phones. We adopted a multi-stage stratified sampling scheme and selected a probability sample of 10,885 adults. Internal consistency reliability of the SF-8 was evaluated with item-total correlations and Cronbach's alphas. Construct validity was assessed with factor analysis. Known-groups validity was examined based on known HRQOL differences in age, gender, income, and overall quality of life.

Results: We showed that SF-8 has very good internal consistency reliability and known-groups validity. Our results also confirmed that the traditional 2-factor structure of SF-8 (physical and mental health) is reasonable among Chinese city residents. Further, we showed that a 3-factor model (physical, mental, and overall health) fit the data better than the traditional 2-factor model.

Conclusions: This study is the first to confirm the traditional 2-factor structure of SF-8 using a large, representative sample from China. We have shown that the SF-8 Chinese version is feasible, reliable, and valid. Our findings support the use of the SF-8 summary scores for assessing general HRQOL among Chinese. Future studies may further explore the possibility of a 3-factor structure for the SF-8 among the Chinese population.