Preliminary diagnostic guidelines for macrophage activation syndrome complicating juvenile idiopathic arthritis

Objective To develop diagnostic guidelines for macrophage activation syndrome (MAS) complicating systemic juvenile idiopathic arthritis (S-JIA).Study design We followed the classification criteria approach that is based on the comparison of patients with the index disease with patients with a "confusable" disease. The former group included 74 patients with S-AA-associated MAS reported in the literature or seen by the authors; the latter group included 37 patients with S-JIA who had 51 instances of "high disease activity" seen by the authors. The relative power of clinical, laboratory, and histopathologic variables in discriminating patients with MAS from patients with high disease activity was evaluated by calculating the sensitivity rate, specificity rate, area under the receiver operating characteristic curve, and diagnostic odds ratio (DOR). The combinations of variables that led to best separation between patients and control subjects were identified through "the number of criteria...