Multisystem inflammatory syndrome in children (MIS-C) may be more common and severe than previously reported, and involves more racial disparities in outcomes than those in COVID-19, according to study results published in JAMA Network Open.
The researchers sought to compare outcomes across MIS-C and COVID-19 across 4057 hospitals in 31 states using all-payer billing data and the new International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Clinical Modification (ICD-10-CM) code.
Researchers aimed to evaluate all COVID-19- and MIS-C-related hospitalizations in individuals younger than 21 years using the data from the Agency for Healthcare Research and Quality 2021 Healthcare Cost and Utilization Project.
The main study outcomes and measures included complications, adverse medical outcomes (AMEs), costs, and Social Vulnerability Index. Two clinical outcomes, including inpatient deaths and AMEs, were studied, specifically with regard to glucocorticoids and immunoglobulin.
A total of 4107 individuals with MIS-C and 23,686 patients with COVID-19 without MIS-C were included in the study. Among those with MIS-C, the median age was 9 years; 59.5% were boys and 38.1% were White. Among those with COVID-19 but without MIS-C, the median age was 15 years; 54.4% were girls and 44.1% were White.
Overall, 1.48 (95% CI, 1.35-1.62) MIS-C hospitalizations per 100,000 children per month were reported, ranging from 0.97 hospitalizations per 100 children for White patients and 1.99 hospitalizations per 100 children for Black patients.
Outcomes worsened as the number of organ system dysfunctions increased from 2 to 8 organs. Deaths associated with MIS-C increased from less than 1% to 5.8% and from less than 1% to 17.2% for COVID-19 (P =.001).
In addition, AMEs associated with MIS-C increased from 4.9% to 17.8% and from 1.2% to 13.4% for COVID-19. The median length of hospital stay increased from 4 to 8 days for MIS-C and from 3 to 16 days for COVID-19.
Median costs increased from $16,225 to $53,359 for MIS-C and from $6474 to $98,643 for COVID-19.
With an increase in organ dysfunction, the percentage of MIS-C cases reported in Black children doubled — from 16.2% to 31.7% (P =.001) — but remained unchanged for COVID-19. Moreover, hospitalizations for MIS-C among Black vs White patients increased by 1 day (P =.01).
Study limitations included the fact that some cases billed as MIS-C do not fulfill the definition of MIS-C by the US Centers for Disease Control and Prevention (CDC) and that some billing data on MIS-C cases may not fit the CDC definition.
Overall, study results showed that MIS-C hospitalizations were more common than previously reported; MIS-C was more severe than commonly believed; racial and ethnic disparities in outcomes emerged with MIS-C, but not with COVID-19; and Black children in more vulnerable socioeconomic areas experienced greater severity in MIS-C outcomes, but not in COVID-19 outcomes.
The study authors concluded that “The findings of this study suggest that relying on mean outcomes for MIS-C from past studies can be misleading, since outcomes and disparities varied widely with the number of multiorgan dysfunctions.”
Disclosure: One of the study authors has declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of the author’s disclosures.
Encinosa W, Moon K, Figueroa J, Elias Y. Complications, adverse drug events, high costs, and disparities in multisystem inflammatory syndrome in children vs COVID-19. JAMA Netw Open. Published online January 5, 2023. doi:10.1001/jamanetworkopen.2022.44975