Timed Up and Go test is predictive of Patient-Reported Outcomes Measurement Information System physical function in patients awaiting total knee arthroplasty.

Background: The Patient Reported Outcomes Measurement Information System (PROMIS) Computerized Adaptive Test (CAT) physical function rapidly assesses self-reported function capability. The Timed Up and Go (TUG) test is often used in clinical practice, but administration may be impeded by space and patient limitations. PROMIS CAT can potentially address these limitations, but we lack evidence if TUG and health indicators are predictors of PROMIS CAT. This study assessed whether TUG, body mass index (BMI), numeric pain rating scale (NPRS), and smoking status were predictors of PROMIS CAT in total knee arthroplasty (TKA) candidates.

Methods: Sixty-five TKA candidates completed the PROMIS CAT physical function test using an iPad application. TUG, NPRS, BMI, and smoking status were obtained at the clinic visit or from medical records. Univariate and multiple regression analyses identified the strongest predictors of PROMIS CAT.

Results: TUG was the best predictor of PROMIS CAT physical function based on simple regression (r = -0.43, 95% CI = -0.62 to -0.20) or multiple regression (  = -0.45, 95% CI = -0.73 to -0.17) analyses. BMI and NPRS did not incrementally help predict the PROMIS score beyond TUG. Smoking status did not contribute to the prediction of the PROMIS CAT score.

Conclusions: The findings suggest that the PROMIS CAT physical function is not a surrogate for the TUG performance-based measure in candidates for TKA. However, TUG was the best predictor of PROMIS physical function compared with BMI, NPRS, and smoking status. Clinicians should consider both patient-reported and performance-based measures when evaluating function for TKA outcomes.