ACR/EULAR Classification Criteria

ACR/EULAR classification criteria

The American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR) have codeveloped classification criteria for identifying MAS in patients with sJIA.¹

A febrile patient with known or suspected sJIA is classified as having MAS if they have:
Ferritin levels >684 ng/mL and any 2 of the following lab abnormalities:

Platelet count (PLT) ≤181 x 10⁹/L

Aspartate aminotransferase >48 U/L

Triglycerides >156 mg/dL

Fibrinogen ≤360 mg/dL

Underlying rheumatic disease can contribute to abnormal lab values, so monitoring the trends of testing results may be more helpful for identifying MAS than absolute values.^2,3

The MS score⁴

Using the 2016 ACR/EULAR classification as a starting point, the MAS/sJIA (MS) score introduces weighted clinical and laboratory variables to assess the probability that a patient with sJIA has MAS.

The equation to calculate the MS score is:

CNS involvement × 2.44 + hemorrhagic manifestations × 1.54 + arthritis × (−1.30) + PLT × (−0.003) + LDH × 0.001 + fibrinogen × (−0.004) + ferritin × 0.0001

For the clinical features of CNS involvement, hemorrhagic manifestations, and active arthritis, a score of 0 or 1 is placed in the formula based on whether they are absent or present, respectively.

The remaining laboratory features should be placed in the formula with their observed values in the units below:

PLT, x 10⁹/L

LDH, U/L

Fibrinogen, mg/dL

Ferritin, ng/mL

In a febrile patient with known or suspected sJIA, the diagnosis of MAS should be considered if the MS score is ≥−2.1.

Signs and symptoms

See how MAS can manifest in patients.

Learn the signs

Managing MAS

Learn about the management strategies for MAS.

Explore management

References: 1. Ravelli A, Minoia F, Davì S, et al. 2016 classification criteria for macrophage activation syndrome complicating systemic juvenile idiopathic arthritis: a European League Against Rheumatism/American College of Rheumatology/Paediatric Rheumatology International Trials Organisation Collaborative Initiative. Arthritis Rheumatol. 2016;68(3):566-576. doi:10.1002/art.39332 2. Minoia F, Davì S, Horne A, et al. Clinical features, treatment, and outcome of macrophage activation syndrome complicating systemic juvenile idiopathic arthritis: a multinational, multicenter study of 362 patients. Arthritis Rheumatol. 2014;66(11):3160-3169. doi:10.1002/art.38802 3. Carter SJ, Tattersall RS, Ramanan AV. Macrophage activation syndrome in adults: recent advances in pathophysiology, diagnosis and treatment. Rheumatology (Oxford). 2019;58(1):5-17. doi:10.1093/rheumatology/key006 4. Minoia F, Bovis F, Davì S, et al. Development and initial validation of the MS score for diagnosis of macrophage activation syndrome in systemic juvenile idiopathic arthritis. Ann Rheum Dis. 2019;78(10):1357-1362. doi:10.1136/annrheumdis-2019-215211

ACR/EULAR classification criteria