Validity, reliability, and responsiveness of the Self-reported Foot and Ankle Score (SEFAS) in forefoot, hindfoot, and ankle disorders.

Background and purpose - The self-reported foot and ankle score (SEFAS) is a questionnaire designed to evaluate disorders of the foot and ankle, but it is only validated for arthritis in the ankle. We validated SEFAS in patients with forefoot, midfoot, hindfoot, and ankle disorders. Patients and methods - 118 patients with forefoot disorders and 106 patients with hindfoot or ankle disorders completed the SEFAS, the foot and ankle outcome score (FAOS), SF-36, and EQ-5D before surgery. We evaluated construct validity for SEFAS versus FAOS, SF-36, and EQ-5D; floor and ceiling effects; test-retest reliability (ICC); internal consistency; and agreement. Responsiveness was evaluated by effect size (ES) and standardized response mean (SRM) 6 months after surgery. The analyses were done separately in patients with forefoot disorders and hindfoot/ankle disorders. Results - Comparing SEFAS to the other scores, convergent validity (when correlating foot-specific questions) and divergent validity (when correlating foot-specific and general questions) were confirmed. SEFAS had no floor and ceiling effects. In patients with forefoot disorders, ICC was 0.92 (CI: 0.85-0.96), Cronbach's α was 0.84, ES was 1.29, and SRM was 1.27. In patients with hindfoot or ankle disorders, ICC was 0.93 (CI: 0.88-0.96), Cronbach's α was 0.86, ES was 1.05, and SRM was 0.99. Interpretation - SEFAS has acceptable validity, reliability, and responsiveness in patients with various forefoot, hindfoot, and ankle disorders. SEFAS is therefore an appropriate patient- reported outcome measure (PROM) for these patients, even in national registries.