CDC updates case definition for MIS-C
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The CDC and Council of State and Territorial Epidemiologists published a revised case definition of multisystem inflammatory syndrome in children, a potentially serious complication of SARS-CoV-2 infection.
Writing in MMWR Recommendations and Reports, the authors of the updated definition noted that the CDC’s 2020 definition of MIS-C — as the condition is known — was not reviewed or voted on by the Council of State and Territorial Epidemiologists, and that numerous other definitions exist, including one written by WHO.
“These definitions differed with respect to patient age limits, fever duration, and organ system involvement,” the authors wrote.
They said it is challenging to develop a case definition of MIS-C for national surveillance “because of a lack of a confirmatory diagnostic laboratory test or pathognomonic clinical features that distinguish MIS-C from COVID-19 or other pediatric hyperinflammatory syndromes such as Kawasaki disease.”
“As a result,” they wrote, “the 2020 CDC MIS-C case definition is complex, relying on combinations of clinical features and supporting laboratory tests to establish inclusion criteria.”
The CDC convened two teleconferences in July and August 2021, asking experts to provide feedback on the case definition criteria. In a summary sent to reporters, the CDC said the new definition “is intended to help reduce misclassification and complexity and will be used to monitor MIS-C epidemiology and trends.”
The new definition removes a required duration of subjective or measured fever, narrows the signs and symptoms that qualify as clinical criteria, and adds a time frame for receipt of a positive COVID-19 test relative to MIS-C illness: up to 60 days before or during hospitalization.
With the new definition, the CDC said that of 9,190 patients in the U.S. who were previously reported as having MIS-C before Aug. 31, 2022, a total of 325 were excluded who did not meet the criteria.
The new definition for voluntarily reporting patients with MIS-C takes effect on Jan. 1, 2023.