ARE DIAGNOSTIC GUIDELINES FOR SYSTEMIC JIA-ASSOCIATED MAS OR HAEMOPHAGOCYTIC LYMPHOHISTIOCYTOSIS SUITABLE TO IDENTIFY MAS IN PATIENTS WITH JUVENILE SLE?

Background: Macrophage activation syndrome (MAS) has been increasingly reported in patients with juvenile SLE (JSLE). Diagnosis of MAS in JSLE may be challenging because it may mimic the underlying disease or an infectious complication. However, no diagnostic guidelines for MAS complicating JSLE exist. It is unclear whether preliminary diagnostic guidelines for MAS complicating SJIA or diagnostic guidelines for hemophagocytic lymphohistiocytosis (HLH) are suitable to detect MAS in patients with SLE. Objectives: To investigate the applicability of diagnostic guidelines for SJIA-associated MAS or HLH in patients with JSLE who developed MAS. The study is presented on behalf of the Lupus Working Group of PRES. Methods: In this multinational study, 38 patients with JSLE and MAS were collected by paediatric rheumatologists in 4 continents: 20 patients had demonstration of macrophage hemophagocytosis in the bone marrow aspirate (``definite'' MAS) and 18 patients lacked this demonstration (``probable'' MAS). Clinical and laboratory features of patients with MAS were contrasted to those of 33 patients with active JSLE without MAS. Frequency of fulfillment of SJIA-MAS and HLH guidelines in patients with MAS and active JSLE was compared. Sensitivity and specificity of guidelines in discriminating MAS from active JSLE was assessed. Results: Patients with definite and probable MAS were combined as they were comparable for most clinical and laboratory features. The table shows frequency of fulfillment, sensitivity and specificity of diagnostic guidelines in patient samples. The chief reasons for fulfilling SJIA-MAS guidelines among 22 patients with active JSLE without MAS were the presence of WBC count < 4 x 10/L (86.4%) and platelet count < 262 x 10/L (81.8%). The leading reasons for 11 patients with JSLE not meeting HLA criteria were lack of splenomegaly (100%), cytopenia affecting 2/3 cell lines (88.9%), and bone marrow confirmation of hemophagocytosis (72.7%). GuidelinesJSLE-MASActive SLEP valueSensitivitySpecificity SJIA-MAS36/36 (100%)22/32 (71.0%)0.0005100%29% HLH22/33 (66.7%)0/32/0.0%)< 0.000166.7%100% Conclusion: Neither SJIA-MAS guidelines, nor HLH guidelines demonstrated sufficient diagnostic sensitivity and specificity to enable their use to diagnose MAS in patients with JSLE. Specificity of SJIA-MAS guidelines was hampered by the high threshold for cytopenia and its frequent presence in active JSLE, whereas reduced sensitivity of HLH guidelines was largely due to the stringent definition of cytopenia and the requirement of tissue confirmation of hemophagocytosis. Disclosure of Interest: None declaredCitation: Annals of the Rheumatic Diseases, volume 68, supplement 3, year 2009, page 298Session: Paediatric rheumatology (Poster Presentations )