Normative Laboratory Value Ranges in Pediatric Patients Who Underwent Evaluation for MIS-C.

Background and Objectives: Diagnosis of multisystem inflammatory syndrome in children (MIS-C) is challenging due to symptom overlap with other common conditions. The primary objective of this multicenter study was to establish normative laboratory values in MIS-C patients and compare to patients evaluated for MIS-C who had other final diagnoses. Methods: Five hospitals reviewed records of a cohort of patients 6 months to 18 years old who were evaluated for MIS-C between March 31 Results: Of the 1319 patients that were evaluated for MIS-C at presentation, 293 (22.2%) received a final diagnosis of MIS-C. MIS-C patients had statistically significant differences in laboratory values including D-dimer, ferritin, fibrinogen, troponin, and brain natriuretic peptide when compared to patients evaluated for MIS-C but subsequently diagnosed with other conditions. The most common non-MIS-C diagnoses within this cohort were viral illnesses (26.7%), acute COVID-19 (12.0%), pyelonephritis (6.4%), fever of unknown origin (4.9%), pneumonia (4.7%), gastroenteritis (4.7%), Kawasaki disease (3.7%), other bacterial infections, (3.1%), rheumatologic conditions (3.1%), and sepsis (2.8%). Conclusions: Many patients who underwent laboratory evaluation for MIS-C during the COVID-19 pandemic received a final diagnosis other than MIS-C. These data may aid pediatricians in differentiating between MIS-C and other febrile conditions as well as reduce unnecessary testing.