ABSTRACT
Introduction: Laboratory features are included in the current case definitions of the multisystem inflammatory syndrome in children (MIS-C) associated with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV2). Objectives: We reviewed the clinical laboratory test values reported in MIS-C, to better characterise the laboratory phenotype. Methods: A comprehensive search of the WHO COVID-19 database was conducted from January to November 2020. The median test values reported in children 0-19 years with MIS-C, were extracted for each laboratory variable reviewed. Random effects meta-analyses were performed and the quantile estimation method used to determine estimates of the pooled median for each variable. The risk of bias was assessed using the QUADAS-2 tool. Results: Twenty-two observational studies were included in the analyses N=831 children. The overall risk of bias was considered moderate with varying heterogeneity between the studies reviewed for each variable (I2 52.4 - 96.63%). The estimated pooled median values which were abnormal included CRP 188.12 mg/L (95% CI 158.54, 217.70), ESR 60.07 mm/hr (95% CI 49.88, 70.26), ferritin (587.63 ng/ml;95% CI (476.29, 698.97), pro-BNP 6927ng/ml (95% CI 794.52, 13061.13), D-dimer 3.03 ng/L (95% CI 2.41, 3.65), absolute neutrophil count 9.61x109L (95% CI 7.72, 11.50), absolute lymphocyte count 0.92 x109/L (95% CI 0.74, 1.10), platelet count 150.82 x109/L (95% CI 135.09, 145.07), albumin 28.89g/L (95% CI 25.56, 32.22) and sodium 132.67mmol/L (95% CI 131.44, 133.89). Limitations The analyses were limited by varying reporting methods and the use of different normal reference ranges across studies. Conclusion: Markers of inflammation, coagulopathy and cardiac dysfunction, were confirmed as important features of the laboratory phenotype of MIS-C. It is necessary however, to further compare the laboratory values of MIS-C to those with COVID-19 and other hyperinflammatory syndromes in children, to develop evidence-based diagnostic criteria.