The 12-item medical outcomes study short form health survey version 2.0 (SF-12v2): a population-based validation study from Tehran, Iran

BACKGROUND: The SF-12v2 is the improved version of the SF-12v1. This study aimed to validate the SF-12v2 in Iran. METHODS: A random sample of the general population aged 18 years and over living in Tehran, Iran completed the instrument. Reliability was estimated using internal consistency and validity was assessed using known-groups comparison and convergent validity. In addition the factor structure of the questionnaire was extracted by performing both exploratory and confirmatory factor analyses (EFA and CFA). RESULTS: In all, 3685 individuals were studied (1887male and 1798 female). Internal consistency for both summary measures was satisfactory. Cronbach's α for the Physical Component Summary (PCS-12) was 0.87 and for the Mental Component Summary (MCS-12) it was 0.82. Known-groups comparison showed that the SF-12v2 discriminated well between men and women and those who differed in age and educational status (P < 0.05). Furthermore, as hypothesized the physical functioning, role physical, bodily pain and general health subscales correlated higher with the PCS-12, while the vitality, social functioning, role emotional and mental health subscales correlated higher with the MCS-12. Finally the exploratory factor analysis indicated a two-factor structure (physical and mental health) that jointly accounted for 59.9% of the variance. The confirmatory factory analysis also indicated a good fit to the data for the two-latent structure (physical and mental health). CONCLUSION: Although the findings could not be generalized to the Iranian population, overall the findings suggest that the SF-12v2 is a reliable and valid measure of health related quality of life among Iranians and now could be used in future health outcome studies. However, further studies are recommended to establish its stability, responsiveness to change, and concurrent validity for this health survey in Iran.