Rockville, MD—For pediatric patients, the most serious post-COVID-19 complication tends to be MIS-C. A new study describes MIS-C as “a relatively novel hyperinflammatory syndrome that customarily arises approximately 1 month after a SARS-CoV-2 infection, sometimes resulting in cardiac complications in previously healthy children.”

The Agency for Healthcare Research and Quality–led study of 4,100 children with MIS-C hospitalizations in 2021 found that the condition was more common and severe than previously reported. In addition, the report in Journal of the American Medical Association Network Open advised that more racial disparities in outcomes were identified than were seen in patients with COVID-19.

“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,” the authors wrote.

Authors of the cross-sectional study determined that as the number of organ systems affected increased from two to six or more:

• Mortality increased from 1% to 6%
• Length of stay doubled from 4 to 8 days
• Adverse medication events increased from 5% to 18%
• The percentage of patients with MIS-C who were black doubled from 16% to 32%.

All of these increases were statistically significant.

“The findings of this study suggest that future efforts should focus on how to prevent MIS-C from progressing to multiple organ system dysfunction,” according to the researchers.

Information on outcomes from MIS-C and COVID-19 was gathered from all 4,057 hospitals in 31 states. Analyses were conducted from February 1, 2022, to October 20, 2022. The researchers focused on 50 complications, adverse medication events, costs, and the Social Vulnerability Index.

The median age of the pediatric patients hospitalized for MIS-C was 9 years, and 59.5% were male. Of those, 38.1% were white. Of the 23,686 individuals with COVID-19 without MIS-C, the median age was 15 years, 54.4% were female, and 44.1% were white.

The study noted that there were 1.48 (95% CI, 1.35-1.62) MIS-C hospitalizations per 100,000 children per month, ranging from 0.97 hospitalizations per 100 children for white and 1.99 hospitalizations per 100 children for black children.

As organ system dysfunction increased:

• Deaths associated with MIS-C increased from less than 1% to 5.8% (95% CI, 3.3%-8.4%) and from less than 1% to 17.2% (95% CI, 11.7%-22.7%) for COVID-19 (P = .001).
• Adverse medication events associated with MIS-C increased from 4.9% (95% CI, 3.8%-6.0%) to 17.8% (95% CI, 13.7%-22.0%) and from 1.2% (95% CI, 1.0%-1.3%) to 13.4% (95% CI, 8.4%-18.3%) for COVID-19.
• The median length of stay for MIS-C increased from 4 (interquartile range [IQR], 2-5) to 8 (IQR, 5-12) days and from 3 (IQR, 2-5) to 16 (IQR, 7-23) days for COVID-19.
• Median costs for MIS-C increased from $16,225 (IQR, $9,244-$26,822) to $53,359 (IQR, $35,920-$86,882) and from $6,474 (IQR, $3,741-$12,103) to $98,643 (IQR, $30,675-$204,956) for COVID-19.

“The percentage of MIS-C cases that were in black children doubled from 16.2% to 31.7% (P = .001) as organ dysfunction increased, remaining unchanged with COVID-19,” the authors wrote. “Hospital stays for MIS-C increased by 1 day (P = .01) for black patients compared with white patients, with black patients moving from the bottom to top quartile of socioeconomic vulnerability, with no disparity with COVID-19.”

The researchers cautioned 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.”

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