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

Abstract

Objective: To determine a core set of measures for youth with 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 (8-18 years) all initiated tumor necrosis factor inhibitor (TNFi) therapy and completed questionnaires, exam, and 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, 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: Patient-Reported Outcomes Measurement Information System (PROMIS) pain interference (SRM: 0.77, SMD: 0.5), the sacroiliac joint inflammation score (SIS; SRM: 1.02, SMD: 0.52), PROMIS mobility (SRM: 0.83, SMD: 0.75), and patient global well-being (SRM: 0.88, SMD: n/a). All overall/composite disease activity measures tested, except the physician global, had high SRM and SMD. Subgroup analysis demonstrated differences by biological sex and overweight status. Improvement in the MRI inflammation score was greater in males. Improvement in the PROMIS pain interference and mobility measures were greater in those with normal BMI.

Conclusions: A set of measures was developed for youth with axJSpA.