Background/Purpose

Patient reported outcome measures (PROs) are used increasingly in clinical care. A framework to interpret scores according to degree of clinical severity would enhance their practical use. Furthermore, use of PROs in evaluation of treatment effectiveness over time requires establishment of minimal important differences (MID) in change scores. 

Methods

We identified clinical severity thresholds and MID for measures of mobility, upper extremity function, fatigue, and pain interference working with patients with juvenile idiopathic arthritis (JIA) and parents of JIA patients using standard setting methodology modified from educational testing. Data from Patient-Reported Outcomes Measurement Information System (PROMIS) item bank longitudinal validation collected on 121 JIA patients was used to develop clinical vignettes across a range of symptom severity. Vignettes were created based on most likely item responses at different levels on the T score metric [mean = 50; SD = 10]. Vignettes were anchored at 5-point intervals (0.5 SDs). Parents and patients participated in separate one-day meetings. Vignettes were ordered and placed on cards. Panelists identified adjacent vignettes considered to represent upper and lower boundaries separating category cut points (i.e., none /mild problems, mild/moderate, moderate/severe). Cut scores were defined as mean score for boundary vignettes. To define MIDs panelists responded to items to represent “just enough improvement to make a difference”. Average change scores served as estimates of MID.

Results

For pain interference, mobility, and upper extremity function patients set higher cut points for severity than parents, typically by 0.5 SD. Parents tended to set higher MID scores than JIA patients. Size of MID varied according to severity classification of the symptom. MIDs estimated by the panelists were typically larger than the MIDs determined using statistical methods.

Conclusion

We used a modified educational standard setting method to estimate clinically relevant cut points to classify severity for PROMIS measures of mobility, upper extremity, fatigue and pain interference. Parallel exercises identified these cut points from the perspectives of patients with JIA and parents of a child with JIA. We explored a novel means of determining MID from the patient/parent perspective. This allows for meaningful interpretation of PROMIS measures in a clinical setting. In summer 2014, the method will be repeated with clinicians serving as panelists. Results will be compared across panel groups. MIDs generated by the 3 panelist groups and those generated statistically from the longitudinal study sample will be compared.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/establishing-clinical-meaning-and-defining-important-differences-in-patient-reported-outcome-measures-of-physical-function-fatigue-and-pain-interference-in-juvenile-idiopathic-arthritis/