In The News: Many Patients Diagnosed With MIS-C Do Not Fit Updated Definition

According to research covered by Healio, nearly one in five patients who were diagnosed with multisystem inflammatory syndrome based on a 2020 definition would not be so diagnosed by an updated CDC definition. The updated version was published in 2022 and took effect on January 1, 2023. Researchers based their study on 119 patients hospitalized between March and November 2020 at a single hospital with a MIS-C diagnosis, as defined in 2020.

The updated, broader definition states MIS-C is “a rare condition associated with SARS-CoV-2 [that] usually occurs 2 to 6 weeks after a child is infected,” and causes “different body parts to become inflamed, including the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal tract.” The prior definition included “the presence of fever” and “systemic inflammation,” and “involvement of at least two organ systems.” In addition to dropping subjective or measured fever, the new definition requires C-reactive protein of 3mg/dL or more to indicate the inflammation.

Part of the change was due to the overlap of MIS-C with other infectious and inflammatory conditions. Previously, children presenting with conditions that could be MIS-C or Kawasaki disease were considered to have MIS-C. In the updated definition, Kawasaki disease is an alternative diagnosis for clinicians to consider. Researchers shared this leads to likely improvements in diagnosis accuracy between the two conditions, though some overlap persists.

The article also shares a second study in Finland that examined long-term impact of MIS-C on vascular changes in children. This study used a third criteria, defined by WHO, to assess children diagnosed with MIS-C. Compared with controls, patients with MIS-C exhibited significantly damaged microcirculation, including lower median microvascular flow index. Study findings remained significant when adjusting for confounders such as age, body mass index, and sex.