Development and validation of minimal disease activity, disease flare, and minimal clinically important difference for children with chronic nonbacterial osteomyelitis using a consensus and data-driven approach.

OBJECTIVES: To create definitions for minimal disease activity (MDA), flare, and minimal clinically important difference (MCID) for chronic nonbacterial osteomyelitis (CNO). It is necessary to establish these criteria before starting clinical effectiveness trials for therapies in CNO. METHODS: Three separate cohorts' samples from an international observational CNO registry were presented to a panel of 20 experts in CNO, including 7 patients/caregivers via online and in-person voting using the group consensus voting technique to define MDA, flare, and MCID, respectively. Experts classified the cases in each cohort as meeting the state for that specific cohort, ie, MDA or not, or flare or not, or meeting MCID or not. A consensus of ≥80% was required. RESULTS: General surveys identified the most important variables to include to define MDA, flare, and MCID. Clinical improvement of ≥30% in these critical parameters and improvement of the CNO Clinical Disease Activity Score by at least 3 were considered meaningful by providers and consensus data. CONCLUSIONS: This study provides the preliminary definitions of MDA, disease flare, and MCID in CNO, which can serve as targets and potential outcomes from treatments. These definitions must now be validated in other cohorts and tested in clinical trials.