Validity of the SF-12 quality of life instrument in patients with retinal diseases

Abstract

Objective To investigate the construct validity and reliability of the SF-12 with the SF-36 composite scores in patients with retinal diseases. Design Cross-sectional study. Participants One thousand eighty-one patients with retinal disease presenting for care at a tertiary referral university-based retina practice. Methods Each patient completed the SF-36 before his or her initial ocular examination. The SF-12 is based on a subset of 12 items from the SF-36. Main outcome measures Physical Composite Score (PCS) and Mental Composite Score (MCS) as determined by the SF-36 and SF-12. Results Eight hundred thirty-nine (78%) of the participants had scorable PCS and MCS scores on the SF-12. No significant differences were found between the SF-36 and SF-12 for the PCS and MCS overall and stratified by the four most frequently occurring disease categories (all P > 0.20). There were statistically significant differences across the disease categories in the mean PCS scores ( P < 0.001) on the SF-36 and SF-12 and the MCS score on the SF-36 ( P = 0.04). The SF-12 PCS and MCS scores were highly correlated with similar indicators (composite scores and subscales) on the SF-36. Conclusions The SF-12 is a valid measure of general health status for ophthalmic research, as long as differences in mental composite scores do not need to be demonstrated between different ocular disease groups. The benefit of reduced administration time makes the SF-12 a recommended general quality-of-life outcomes tool.