Purpose: This study was conducted to determine the minimal clinically important difference (MCID) of the Patient-Reported Outcomes Information System (PROMIS) Physical Function computer adaptive test (CAT) after distal radius fracture. Methods: This study retrospectively analyzed data from 187 adults receiving nonsurgical care for a unilateral distal radius fracture at a single institution between February 2016 and November 2017. All patients completed the PROMIS Physical Function v1.2/2.0 CAT at each visit. At follow-up, patients also completed 2 multiple-choice clinical anchor questions querying their overall response to treatment. The MCID estimate was then calculated with an anchor-based method as the mean PROMIS Physical Function score change for the group reporting mild improvement and with a distribution-based method considering effect sizes of change and the minimum detectable change (MDC). The MCID estimate was examined for the influence of patient age, follow-up interval, and initial PROMIS score. Results: Change in PROMIS Physical Function scores between visits was significantly different between patients reporting no change, mild improvement, and much improvement on the anchor questions. The anchor-based MCID estimate for PROMIS Physical Function was 3.6 points (SD, 8.4). Among patients reporting mild improvement, individual changes in PROMIS Physical Function were not correlated with patient age or time between visits but were moderately negatively correlated with the initial absolute PROMIS Physical Function score. Applying the effect size parameters to our data when patients indicated minimal change, the distribution-based MCID estimate was 4.6 (SD, 1.8). Both the anchor-based and the distribution-based MCID estimates were judged sufficient because they exceeded the MDC value of 2.3. Conclusions: The MCID value for PROMIS Physical Function is estimated between 3.6 and 4.6 in patients treated nonsurgically for distal radius fractures. Clinical improvement is associated with smaller magnitudes of change on PROMIS Physical Function when patients present with better reported function. Clinical relevance: The MCID estimations are needed to determine the clinical relevance of changes in PROMIS scores and to more accurately calculate sample sizes needed for research incorporating PROMIS.
- Distal radius
- minimally clinically important difference
- physical function