Table 1.

Classification criteria for macrophage activation syndrome in known or suspected systemic juvenile idiopathic arthritis. From Ravelli, et al. Ann Rheum Dis 2016;75:481–9; and Ravelli, et al. Arthritis Rheumatol 2016;68:566–76; adapted with permission1,9.

Classification Criteria for MAS

  • Fever AND ferritin > 684 ng/ml

Plus any 2 of the following 4 criteria:

  • Platelet count ≤ 181 × 109/l

  • AST > 48 units/l

  • Triglycerides > 156 mg/dl

  • Fibrinogen ≤ 360 mg/dl

  • MAS: macrophage activation syndrome; AST: aspartate aminotransferase.