Background/Purpose:  Juvenile dermatomyositis (JDM) is a systemic autoimmune disease characterized by chronic skeletal muscle inflammation with weakness and skin involvement. The Paediatric Rheumatology INternational Trials Organisation (PRINTO) and the International Myositis and Clinical Studies Group (IMACS) developed criteria to evaluate response in clinical trials which have been recently updated and validated. We compared the PRINTO 2010 (JDM 2010 response criteria) with PRINTO/IMACS 2016 response criteria (JDM 2016 criteria) for improvement in the PRINTO new onset JDM trial.

Methods: New onset JDM children were randomized to receive either prednisone (PDN) alone or in combination with methotrexate (MTX) or cyclosporine A (CSA). Patients were evaluated at months 6, 12, 18 and 24 with different levels of JDM 2010 criteria (improvement of 20-50-70 or 90% in at least three of the 6 core set measures and worsening <30% in no more than one). The same patients were re-analyzed with the continuous JDM 2016 criteria which evaluate absolute percent change into three categories (total score 0-100): minimal (≥30), moderate (≥45), major (≥70) improvement. Clinical trials data were analyzed according to the intention-to-treat (ITT) principle with patients discontinuing (lack of efficacy, safety, etc.) considered as non-responders from that point onwards.

Results:  139 children were enrolled in the trial: 47 on PDN, 46 on PDN+CSA and 46 on PDN+MTX. The two sets of criteria showed a similar capacity to recognize different levels of improvement of the disease at 6, 12, 18 and 24 months, after treatment with PDN, PDN+CSA or PDN+MTX as shown by the overlapping 95% CI intervals at various time points (Table). In particular, at month 6, 51% patients on PDN versus 72% on PDN+CSA or PDN+MTX achieved at least JDM 2010 20% improvement (p=0.023) as compared to 55% and 74% with the JDM 2016 minimal improvement (p=0.027). At month 24, 38% patients on PDN versus 60% on PDN+CSA or PDN+MTX achieved at least JDM 2010 20% improvement (p=0.016) as opposed to 38% and 61% with JDM 2016 minimal improvement (p=0.012). Kappa agreement between the two criteria with ITT approach were at least in the moderate range (0.61-0.8) as follows: 0.75, 0.75, 0.77, 0.79 at 6-12-18 and 24 months, respectively. The JDM 2016 criteria, similar to the 2010 criteria, confirmed the superior efficacy of combined treatment with PDN+CSA or PDN+MTX versus treatment with PDN alone.   Table 1. 2010 and 2016 improvement criteria after 6, 18 and 24 months of treatment with PDN or PDN+MTX or PDN+CSA (only few examples are reported)

Conclusion:  Both response criteria have shown a similar discrimination in evaluating different levels of improvement in new onset JDM patients treated with 3 alternative treatment strategies.