Background/Purpose: Macrophage Activation Syndrome (MAS) is a severe, life-threatening, complication of rheumatic diseases in childhood, particularly of systemic Juvenile Idiopathic Arthritis (sJIA), occurring in approximately 25% of the patients with sJIA. The mortality rate of MAS is still significantly high. A score that identify sJIA patients who are at high risk to develop MAS would be useful in clinical practice. There are no parameters available to identify from onset sJIA patients with high risk to develop MAS in their disease course.We evaluated whether routine laboratory parameters at disease onset may predict the development of MAS in patients with active sJIA. To define a risk score of MAS for sJIA patients using these parameters.

Methods: Laboratory parameters of disease activity and severity (WBC, N, PLT, Hb, ferritin, AST, ALT, gGT, LDH, TGL, fibrinogen, D-dimerand CRP), were retrospectively evaluated in 56 sJIA patients referred to our Division of Rheumatology from 1998 to 2016 with at least one year of follow-up. Laboratory parameters were evaluated during active sJIA, without MAS, at time of hospitalization (T1) and before treatment for sJIA was started (T2). Patients were divided in two groups:group 1 (patients without history of MAS), group 2 (patients with at least one MAS episode during disease course). In order to calculate a MAS risk score, laboratory parameters, collected at T2, with a statistical significant difference between the two groups of patients were selected.

Results: Fourteen patients, that fulfilled the 2016 classification criteria for MAS [1] at time of sampling, were excluded from the analysis. Therefore, we analyzed laboratory parameters of 42 patients with sJIA, 27 of whom without history of MAS (group 1) and 15 who developed at least one episode of MAS during disease course (group 2). Levels of ferritin, AST, LDH, gGT and TGL, collected at T2, were statistically significant higher in patients with a history of MAS compared to those without a history of MAS. For each of these parameters an arbitrary cut-off was defined. In order to define the final score an arbitrary rate was attributed to each parameter. Sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) were calculated to define the best scoring system. The scoring system with the best sensitivity was chosen (Table 1). A MAS risk score >3 identified 14 out of 15 sJIA patients with a history of MAS and 3 out of 27 sJIA patients without history of MAS.

Table 1. Laboratory parameters and cut-off used to create the MAS risk score in sJIA patients.

Conclusion: We developed an MAS risk score based on routine laboratory parameters that are available worldwide, that can help clinicians to identify these patients early in the disease course. Our results are preliminary and a validation in a larger population is ongoing.

Reference

1. Ravelli A et al. Ann Rheum Dis. 2016 Mar;75(3):481-9.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/risk-score-of-macrophage-activation-syndrome-in-patients-with-systemic-juvenile-idiopathic-arthritis/