Linking FAAM and PROMIS Physical Function Scores: A Crosswalk Study

Within orthopaedic surgery, Patient-Reported Outcomes Measurement Information System (PROMIS) and legacy patient-reported outcomes (PRO) scores are both commonly reported. Although PROMIS and PROs often correlate, mathematical modeling is needed to create linkage tables that can be used for further research and possible clinical applicability. Such studies have been performed in varying orthopaedics subspecialities. However, no linkage study has been performed in foot and ankle research for any PRO metrics.

In this study, we aimed to create linkage tables for PROMIS physical function and Foot and Ankle Ability Measure (FAAM) scores. The FAAM is a valid, legacy PRO used in foot and ankle research. We retrospectively collected FAAM and PROMIS PF scores on 745 patients undergoing surgery. Correlations were performed between FAAM and PROMIS PF scores. Statistical models were then used to link the metrics including linear regression, identity, mean, linear, circle-arc, and equipercentile techniques.

FAAM and PROMIS PF scores were correlated. All linking methods resulted in an ICC of at least 0.57 and an R ² of at least 0.49. Both the linear and equipercentile methods demonstrated an R ² value of 0.93, though the ICC for the equipercentile model was slightly higher than the linear model. The linear model resulted in a lower SE and was therefore used to evaluate population invariance.

No prior studies have linked patient-reported outcomes tools in foot and ankle research. Here, we successfully linked two commonly used metrics (PROMIS PF and FAAM scores). Creating crosswalk tables, we hope, can enhance data comparison in larger-scale orthopaedic foot and ankle research.

Level III, retrospective study.