Circulating Interferon‐α Measured With a Highly Sensitive Assay as a Biomarker for Juvenile Inflammatory Myositis Activity: Comment on the Article by Mathian et al. Issue 1 (23rd November 2019) - Melki, Isabelle; Devilliers, Hervé; Gitiaux, Cyril; Bondet, Vincent; Belot, Alexandre; Bodemer, Christine; Quartier, Pierre; Crow, Yanick J.; Duffy, Darragh; Rodero, Mathieu P.; Bader Meunier, Brigitte