The performance of the diagnostic scoring system or criteria for macrophage activation syndrome in systemic juvenile idiopathic arthritis for adult-onset Still's disease. A multicentre case-control study in China.

OBJECTIVES To evaluate the performance of the diagnostic scoring system/criteria for macrophage activation syndrome (MAS) used in systemic juvenile idiopathic arthritis (sJIA) for adult-onset Still's disease (AOSD). METHODS This retrospective case-control study included AOSD patients with and without MAS from six hospitals in China. The cut-off values that best discriminated MAS from active AOSD were determined by receiver operating characteristic (ROC) curve analysis. The performance of the present diagnostic scoring system/criteria for sJIA-MAS was evaluated in AOSD-associated MAS. The optimal critical value of the ROC curve replaces the relevant indicators of the existing scoring system and different models were tested for sensitivity/specificity. RESULTS A total of 56 AOSD-associated MAS patients (AOSD-MAS) and 112 AOSD patients without MAS matched with age and sex treated at six centres between 2007 and 2017 were enrolled. The 2016 MAS in sJIA classification criteria had an overall sensitivity of 100.0% and specificity of 80.4% for classifying AOSD-MAS. Excluding hypertriglyceridemia and substituting some other criteria with newly obtained cut-off values could increase specificity. An MS score ≥-2.1 yielded a sensitivity of 95.2% and a specificity of 76.6% in classifying AOSD-MAS. ROC curve analysis revealed that a score of -1.74 could best discriminate AOSD-MAS from AOSD without MAS. An MS score ≥-1.74 yielded a sensitivity of 93.5% and a specificity of 92.6% in diagnosing AOSD-MAS (AUC=0.96, 95%CI: 0.93-0.99, p<0.0001). CONCLUSIONS The diagnostic tool for MAS in sJIA with modification appears to apply to AOSD-MAS.