Background: Patient-Reported Outcomes Measurement Information System (PROMIS) measures are used increasingly in clinical care. However, for juvenile idiopathic arthritis (JIA), scores lack a framework for interpretation of clinical severity, and minimally important differences (MID) have not been established, which are necessary to evaluate the importance of change.
Methods: We identified clinical severity thresholds for pediatric PROMIS measures of mobility, upper extremity function (UE), fatigue, and pain interference working with adolescents with JIA, parents of JIA patients, and clinicians, using a standard setting methodology modified from educational testing. Item parameters were used to develop clinical vignettes across a range of symptom severity. Vignettes were ordered by severity, and panelists identified adjacent vignettes considered to represent upper and lower boundaries separating category cut-points (i.e., from none/mild problems to moderate/severe). To define MIDs, panelists reviewed a full score report for the vignettes and indicated which items would need to change and by how much to represent "just enough improvement to make a difference."
Results: For fatigue and UE, cut-points among panels were within 0.5 SD of each other. For mobility and pain interference, cut-scores among panels were more divergent, with parents setting the lowest cut-scores for increasing severity. The size of MIDs varied by stakeholders (parents estimated largest, followed by patients, then clinicians). MIDs also varied by severity classification of the symptom.
Conclusions: We estimated clinically relevant severity cut-points and MIDs for PROMIS measures for JIA from the perspectives of multiple stakeholders and found notable differences in perspectives.
Keywords: Item response theory (IRT); Juvenile idiopathic arthritis; PROMIS; Patient-reported outcomes; Psychometric methods.