Diagnosing MAS

Diagnosing MAS in patients with rheumatic disease

Diagnosing MAS

Macrophage activation syndrome (MAS) is a life-threatening complication of rheumatic disease that can be difficult to diagnose.1 Patients with underlying disease can have different baseline clinical and laboratory characteristics, which may vary significantly compared to the available diagnostic criteria.2,3 Delayed diagnosis and treatment is associated with worse outcomes, so it is critical that MAS is recognized as early as possible.4

Currently, no single set of criteria has been validated for the diagnosis of MAS across all ages and circumstances. However, evidence suggests that monitoring the relative changes from baseline in the common clinical and laboratory features of MAS can help with early recognition.1

ACR/EULAR classification criteria5

The American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR) have
developed classification criteria for identifying MAS in patients with systemic juvenile idiopathic arthritis (sJIA).

A patient with known or suspected sJIA presenting with fever can be classified as having MAS if the following criteria are met:

Ferritin >684 ng/mL and any 2 of the following:

Platelet count ≤181 x 109/L

Aspartate aminotransferase >48 units/L

Triglycerides >156 mg/dL

Fibrinogen ≤360 mg/dL

The MS score and HScore

Other diagnostic criteria include the MS score for identifying MAS in the setting of active sJIA, and the HScore, which is a tool for
diagnosing hemophagocytic syndromes.6,7

MS score icon

MS Score

7 weighted clinical and laboratory variables

The MS score was developed using the same
dataset as the ACR/EULAR classification
criteria but excluding the control sample with
systemic infection, and is used to measure the
probability of MAS in patients with sJIA.6

HScore icon

HScore

9 weighted clinical, biologic and cytologic variables

The HScore measures the probability of a
reactive hemophagocytic syndrome in a
particular patient (associated with infection,
malignancy, or rheumatic disease).7

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