An international consensus survey of diagnostic criteria for macrophage activation syndrome in systemic juvenile idiopathic arthritis.

Objective. To identify candidate diagnostic criteria for macrophage activation syndrome (MAS) complicating systemic juvenile idiopathic arthritis (sJIA) using international consensus formation through a Delphi questionnaire survey. Methods. A questionnaire listing 28 clinical, laboratory, and histopathologic features of MAS elicited by literature review was sent to 505 pediatric rheumatologists worldwide. Respondents were asked to select the 10 features that they felt were most important and useful in the diagnosis of MAS, and to order the 10 selected features by assigning the number 10 to the most important, and ending with 1 as the least important. Results. The response rate was 46% (232 physicians from 47 countries). The items selected by more than 50% of respondents were, in order of frequency, falling platelet count, hyperferritinemia, evidence of macrophage hemophagocytosis in the bone marrow, increased liver enzymes, falling leukocyte count, persistent continuous fever ≥ 38°C, falling erythrocyte sedimentation rate, hypofibrinogenemia, and hypertriglyceridemia. Conclusion. Our process led to identification of features that were felt to be most important as candidate diagnostic criteria for MAS by a large sample of international pediatric rheumatologists.