Validity and reliability of Thai version of the Foot and Ankle Outcome Score in patients with arthritis of the foot and ankle

Abstract

Background: Although the Foot and Ankle Outcome Score (FAOS) is commonly used in several languages for a variety of foot disorders, it has not been validated specifically for foot and ankle arthritic conditions. The aims of the present study were to translate the original English FAOS into Thai and to evaluate the validity and reliability of the Thai version of the FAOS for the foot and ankle arthritic conditions.

Methods: The original FAOS was translated into Thai using forward-backward translation. The Thai FAOS and validated Thai Short Form-36 (SF-36^®) questionnaires were distributed to 44 Thai patients suffering from arthritis of the foot and ankle to complete. For validation, Thai FAOS scores were correlated with SF-36 scores. Test-retest reliability and internal consistency were also analyzed in this study.

Results: The Thai FAOS score demonstrated sufficient correlation with SF-36 total score in Pain (Pearson's correlation coefficient (r)=0.45, p=0.002), Symptoms (r=0.45, p=0.002), Activities of Daily Living (ADL) (r=0.47, p=0.001), and Quality of Life (QOL) (r=0.38, p=0.011) subscales. The Sports and Recreational Activities (Sports & Rec) subscale did not correlate significantly with the SF-36^® (r=0.20, p=0.20). Cronbach's alpha, a measure of internal consistency, for the five subscales was as follows: Pain, 0.94 (p<0.001); Symptoms, 0.58 (p<0.001); ADL, 0.96 (p<0.001); Sports & Rec, 0.79 (p<0.001); and QOL, 0.93 (p<0.001). The intraclass correlation coefficient (ICC) of a major subscale of ADL, containing 17 items, was significant at 0.33 (p=0.013; 95% confidence interval, 0.04-0.57).

Conclusion: The Thai FAOS demonstrated sufficient levels of construct and content validity for the evaluation of foot and ankle arthritis. Although reliability was satisfactory for the major subscale ADL, it was not sufficient for the minor subscales. Our findings suggest that it can be used as a disease-specific instrument to evaluate foot and ankle arthritis and can complement other reliable outcome surveys.

Keywords: Foot and Ankle Outcome Score (FAOS); Patient-reported; Questionnaire; Reliability; Short Form 36 General Health Outcome (SF-36(®)); Validity.