Correlation of SF-36 and SF-12 Component Scores in Patients With Diabetic Foot Disease

The assessment of patient outcomes is becoming increasingly important in all areas of medicine, including foot and ankle surgery. The Medical Outcomes Study Short Form 36-item (SF-36) is widely used as a generic measure of quality of life; however, patients often find answering 36 questions cumbersome. Consequently, the Short Form 12 (SF-12) was developed. We hypothesized that the agreement between the SF-12 and SF-36 component scores would be substantial in patients with diabetic foot disease. We retrospectively reviewed the data from 300 patients with diabetes mellitus (DM) and foot and ankle pathology who completed the SF-36 questionnaire. Of the 300 patients, 155 (51.7%) had problems directly related to complications of DM and 145 (48.3%) had routine foot complaints that were unrelated to complications of DM. The 12 questions of the SF-12 were abstracted from the SF-36. The overall median score for the SF-36 physical component summary was 34.70 compared with the overall SF-12 physical component summary of 36.75 (p = .04). The intraclass correlation coefficient was 0.93688. The overall median score for the SF-36 mental component summary was 52.40 compared with the overall SF-12 mental component summary of 51.25 (p = .34). The intraclass correlation coefficient was 0.95449. Substantial agreement was observed when comparing the component scores of the SF-12 and the SF-36. From our study results of 300 patients with DM, it appears that the SF-36 and SF-12 are comparable outcome instruments for use with patients with diabetic foot disease.