Evaluation of the Validity of the AOFAS Clinical Rating Systems by Correlation to the SF-36

Abstract

This study evaluates the validity of the AOFAS Clinical Rating Systems by examining their level of correlation to the Medical Outcomes Study Short Form-36 (SF-36) in patients with foot and ankle complaints. The SF-36 is an extensively validated outcomes tool that has been used as a benchmark in examining the validity of outcomes instruments designed for the upper extremity, knee, shoulder, and general orthopaedic conditions. The study sample was 91 patients seen at the foot and ankle clinic of a university-based orthopaedic practice. Patients were administered both the AOFAS Clinical Rating Systems and SF-36 instruments. Pearson correlation coefficients of the AOFAS scores to the SF-36 sub-scales ranged from 0.02 to 0.36 in the overall study population. Correlation was higher for the sub-set of patients with ankle-hindfoot disorders (0.11 to 0.53) than patients with forefoot disorders (-0.05 to 0.25). The low levels of correlation seen in this study suggest poor construct validity of the AOFAS Clinical Rating Systems.

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“…He concluded the AOFAS cannot produce reliable data and score values obtained by parametric statistics must be interpreted with care [16]. SooHoo et al [37] correlated the AOFAS score with the SF-36 and found only weak associations, suggesting poor construct validity of this instrument. Two other studies investigating the association between the AOFAS and the generic questionnaires QUALY and MFA also found only low correlations between these instruments [26,34].…”

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“…SooHoo et al (15) assessed the correlation of the four AOFAS scales with the SF-36 questionnaire and, despite of the low correlation, they found a higher consistency between the Pain domain of the SF-36 and the AOFAS Ankle-Hindfoot Scale. Although Vitality, Social Aspects, and Mental Health domains presented statistically significant values, we suggest that such correlations are not taken into account, once there are no questions corresponding to these items in the AOFAS ankle-hindfoot assessment scale.…”

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“…The AOFAS ankle-hindfoot score, as a complete score, has been shown to be valid 265,364,447 . The score has shown good responsiveness over time in two studies, with reported effect sizes of 1.69 265 and 1.12 365 .…”

“…Furthermore, the subscale pain is heavily weighted (40 points), and there is a 20-point diff erence between rating pain as severe (almost always present) and moderate (daily). To establish reliability, validity, and responsiveness, the scale has been evaluated related to a wide spectrum of diagnoses, such as general ankle-hindfoot complaints 364 , pending ankle or foot surgery 192 , surgically treated calcaneal fractures 447 and end-stage ankle arthritis 265 . However, there is no study that has evaluated the psychometric properties in patients with talar OCD.…”