COMMENT & RESPONSE In Reply In their Letter, Vulsteke et al highlight an unmet need: the harmonization of myositis specific autoantibody (MSA) detection. We recently showed that patients with myositis can be classified into 4 homogeneous subgroups 1 and that MSA plays a major role in predicting patients will be in a specific subset. As mentioned by Vulsteke et al, our study did not include a control group of patients with noninflammatory myopathies. This was because our primary aim was to identify homogeneous subgroups of patients with myositis using unsupervised statistical methods based on a complete data set (with no missing data) comprising, among others, MSA. Furthermore, MSAs are now validated diagnostic criteria for immune-mediated necrotizing myopathies 2 and have been recently recognized as diagnostic criteria for dermatomyositis (239th European NeuroMuscular Center International Workshop, Amsterdam, December 14-16, 2018). In the American College of Rheumatology/European League Against Rheumatism diagnostic criteria for myositis, 3 the presence of anti-Jo1 antibody is the item assigned with the heaviest weighted score, but the weakness of this criterium is that no other MSAs were considered. 3