J Foot Ankle Surg 2007 Mar-Apr;46(2):65-74
Department of Orthopaedic Surgery, Kettering General Hospital, United Kingdom.
This study evaluates the criterion validity of the subjective component of the American Orthopaedic Foot and Ankle Society (AOFAS) clinical rating scales by correlating scores obtained with these rating scales to scores obtained with the Foot Function Index (FFI) in patients with foot and ankle conditions. To date, the AOFAS scoring scales have not been shown to provide valid information despite their popularity. The FFI, on the other hand, has previously been shown to provide valid information in regard to conditions affecting the foot and ankle. A moderately strong inverse criterion validity correlation (Pearson correlation coefficient = -0.68) was shown when preoperative patients were administered both the AOFAS and FFI questionnaires, and the resultant scores were compared. Test-retest reliability measurements showed no significant difference (P = .27) between preoperative AOFAS scale scores measured at least 2 weeks apart. Construct validity was shown (P = .006) when dependent preoperative and postoperative (at least 3 months) AOFAS scale scores were compared, indicative of the clinical rating scales' ability to discriminate and predict quality of life related to foot and ankle conditions. The moderate level of correlation, satisfactory degree of reliability, and responsiveness (ability to distinguish differences between preoperative and postoperative conditions in the same patient) observed in this study suggest that the subjective component of the AOFAS clinical rating scales provides quality-of-life information that conveys acceptable validity regarding conditions affecting the foot and ankle.