Is SF-12 a valid and reliable measurement of health-related quality of life among adults with Marfan syndrome? A confirmatory study.

INTRODUCTION: The structural validity and reliability of the Short-Form Health Survey 12 (SF-12) has not yet been tested in adults with the Marfan syndrome (MFS). This gap could undermine an evidence-grounded practice and research, especially considering that the need to assess health-related quality of life in patients with MFS has increased due to the improved life expectancy of these patients and the need to identify their determinants of quality of life. For this reason, this study aimed to confirm the dimensionality (structural validity) of the SF-12, its concurrent validity, and its reliability (internal consistency). METHODS: We performed a cross-sectional study in a convenience sample of 111 Italian adults with MFS, collecting anamnestic and socio-demographic information, the SF-12, and short-form Health Survey 36 (SF-36). A confirmatory factor analysis was performed to verify whether the items of SF-12 related to physical restrictions, physical functioning, and bodily pain were retained by the physical summary component of the SF-12. The items referred to the role limitations due to emotional issues, social functioning, and mental health were retained by the mental summary component (MCS12). SF-36 was used to assess the concurrent validity of SF-12, hypothesizing positive correlations among the equivalent summary scores. RESULTS: The two-factor structural solution resulted in fitting the sample statistics adequately. The internal consistency was adequate for the two factors. Furthermore, the physical and mental summary scores of the SF-36 were positively correlated with their equivalent summary scores derived from the SF-12. CONCLUSIONS: This study confirmed the factor structure of the SF-12. Therefore, the use of SF-12 in clinical practice and research for assessing the health-related quality of life among adults with MFS is evidence-grounded. Future research is recommended to determine whether the SF-12 shows measurement invariance in different national contexts and determine eventual demographic variation in the SF-12 scores among patients with MFS.