Differential item functioning to validate setting of delivery compatibility in PROMIS-global health

Purpose Patient-reported outcomes measures (PROMs) such as PROMIS are increasingly utilized in healthcare to assess patient perception and functional status, but the effect of delivery setting remains to be fully investigated. To our knowledge, no current study establishes the absence of differential item functioning (DIF) across delivery setting for these PROMIS- Global Health (PROMIS-GH) measures among orthopedic patients. We sought to investigate the correlation of PROMIS-GH scores across in-clinic versus remote delivery by evaluating DIF within the Global Physical Health (GPH) and Global Mental Health (GMH) items. We hypothesize that the setting of delivery of the GPH and GMH domains of PROMIS-GH will not impact the results of the measure, allowing direct comparison between the two delivery settings. Methods Five thousand and seven hundred and eighty-five complete PROMIS-Global Health measures were analyzed retrospectively using the ‘Lordif’ package on the R platform. DIF was measured for GPH and GMH domains across setting of response (in-clinic vs remote) during the pre-operative period, immediate post-operative period, and 1-year post-operative period using Monte Carlo estimation. McFadden pseudo-R2 thresholds (> 0.02) were used to assess the magnitude of DIF for individual PROMIS items. Results No GPH or GMH items contained in the PROMIS-GH instrument yielded DIF across in-clinic vs remote delivery setting during the pre-operative, immediate post-operative, or 1-year post-operative window. Conclusion The GPH and GMH domains within the PROMIS-GH instrument may be delivered in the clinic or remotely with comparable accuracy. This cross-delivery setting validation analysis may aid to improve the quality of patient care by allowing mixed platform PROMIS-GH data tailored to individual patient circumstance.