Plasma protein biomarkers distinguish Multisystem Inflammatory Syndrome in Children (MIS-C) from other pediatric infectious and inflammatory diseases

Background Multisystem inflammatory syndrome in children (MIS-C) is a rare but serious hyperinflammatory complication following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The mechanisms underpinning the pathophysiology of MIS-C are poorly understood. Moreover, clinically distinguishing MIS-C from other childhood infectious and inflammatory conditions, such as Kawasaki Disease (KD) or severe bacterial and viral infections is challenging due to overlapping clinical and laboratory features. We aimed to determine a set of plasma protein biomarkers that could discriminate MIS-C from those other diseases. Methods Seven candidate protein biomarkers for MIS-C were selected based on literature and from whole blood RNA-Sequencing data from patients with MIS-C and other diseases. Plasma concentrations of ARG1, CCL20, CD163, CORIN, CXCL9, PCSK9 and ADAMTS2 were quantified in MIS-C (n=22), KD (n=23), definite bacterial (DB; n=28) and viral (DV, n=27) disease, and healthy controls (n=8). Logistic regression models were used to determine the discriminatory ability of individual proteins and protein combinations to identify MIS-C, and association with severity of illness. Results Plasma levels of CD163, CXCL9, and PCSK9 were significantly elevated in MIS-C with a combined AUC of 86% (95% CI: 76.8%-95.1%) for discriminating MIS-C from other childhood diseases. Lower ARG1 and CORIN plasma levels were significantly associated with severe MIS-C cases requiring oxygen, inotropes or with shock. Conclusion Our findings demonstrate the feasibility of a host protein biomarker signature for MIS-C and may provide new insight into its pathophysiology.