Core Set of Responsive and Discriminatory Measures for Use in Pragmatic Trials of Youth With Axial Juvenile Spondyloarthritis.

OBJECTIVE

The objective of this study was to determine a core set of measures for youth with juvenile spondyloarthritis and axial disease (axJSpA), using the juvenile arthritis working group Outcome Measures in Rheumatology framework.

METHODS

This was a prospective multicenter study of youth with axJSpA. Participants (aged 8-18 years) all initiated tumor necrosis factor inhibitor (TNFi) therapy and completed questionnaires, examinations, and magnetic resonance imaging (MRI) at baseline and 12 weeks. Responsiveness and discrimination were assessed using standardized response mean (SRM) and standardized mean difference (SMD). For highly correlated (r > |0.80|) items within domains, larger SRM and SMD were prioritized, and minimal clinically important improvement was determined for each.

RESULTS

Of the evaluable cohort (N = 57), 68.4% were male, and the median age was 15.3 years; 70.2% of youth treated with TNFi had clinical response (change ≥2 in patient global assessment). Although 58% had continued MRI inflammation, 77% of those patients reported moderate clinical improvement. The final axJSpA core set contained the following: Patient-Reported Outcomes Measurement Information System (PROMIS) pain interference (SRM 0.77, SMD 0.5), the sacroiliac joint inflammation score (SRM 1.02, SMD 0.52), PROMIS mobility (SRM 0.83, SMD 0.75), and patient global well-being (SRM 0.88, SMD not applicable). All overall and composite disease activity measures tested, except the physician global assessment, had high SRM and SMD. Subgroup analysis demonstrated differences by biologic sex and overweight status. Improvement in the MRI inflammation score was greater in male patients. Improvement in the PROMIS pain interference and mobility measures was greater in those with normal body mass index.

CONCLUSION

A set of measures was developed for youth with axJSpA.