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Multisystem inflammatory syndrome in children (MIS-C) 1 manifests as immune dysregulation after SARS-CoV-2 infection. 2 The syndrome has no pathognomonic features. Thus, the diagnostic criteria of the Royal College of Paediatrics and Child Health (RCPCH), the Centers for Disease Control and Prevention (CDC) and the World Health Org anization (WHO) differ, but they all include fever, evidence of systemic inflammation and involvement of at least 1 organ or system. 3 Our primary objective was to assess initial clinical or laboratory features that predict severe illness in MIS-C. We also sought to explore changes in overall disease severity and cardiac involvement over time as it was the impression of many investigators that severity of MIS-C increased through pandemic waves.

in Canada. COVID-19-related abnormalities in the hematologic characteristics among inpatient children. Results of the PICNIC Registry. ISTH 2021 Congress. https://abstracts.isth.org/abstract/covid-19related-abnormalities-in-the-hematologiccharacteristics-among-inpatient-childrenresults-of-the-picnic-registry/

ObjectiveTo identify risk factors for severe disease in children hospitalised for SARS-CoV-2 infection.DesignMulticentre retrospective cohort study.Setting18 hospitals in Canada, Iran and Costa Rica from 1 February 2020 to 31 May 2021.PatientsChildren<18 years of age hospitalised for symptomatic PCR-positive SARS-CoV-2 infection, including PCR-positive multisystem inflammatory syndrome in children (MIS-C).Main outcome measureSeverity on the WHO COVID-19 Clinical Progression Scale was used for ordinal logistic regression analyses.ResultsWe identified 403 hospitalisations. Median age was 3.78 years (IQR 0.53–10.77). At least one comorbidity was present in 46.4% (187/403) and multiple comorbidities in 18.6% (75/403). Eighty-one children (20.1%) met WHO criteria for PCR-positive MIS-C. Progression to WHO clinical scale score ≥6 occurred in 25.3% (102/403). In multivariable ordinal logistic regression analyses adjusted for age, chest imaging findings, laboratory-confirmed bacterial and/or viral coinfection, and MIS-C diagnosis, presence of a single (adjusted OR (aOR) 1.90, 95% CI 1.13 to 3.20) or multiple chronic comorbidities (aOR 2.12, 95% CI 1.19 to 3.79), obesity (aOR 3.42, 95% CI 1.76 to 6.66) and chromosomal disorders (aOR 4.47, 95% CI 1.25 to 16.01) were independent risk factors for severity. Age was not an independent risk factor, but different age-specific comorbidities were associated with more severe disease in age-stratified adjusted analyses: cardiac (aOR 2.90, 95% CI 1.11 to 7.56) and non-asthma pulmonary disorders (aOR 3.07, 95% CI 1.26 to 7.49) in children<12 years old and obesity (aOR 3.69, 1.45–9.40) in adolescents≥12 years old. Among infants<1 year old, neurological (aOR 10.72, 95% CI 1.01 to 113.35) and cardiac disorders (aOR 10.13, 95% CI 1.69 to 60.54) were independent predictors of severe disease.ConclusionWe identified risk factors for disease severity among children hospitalised for PCR-positive SARS-CoV-2 infection. Comorbidities predisposing children to more severe disease may vary by age. These findings can potentially guide vaccination programmes and treatment approaches in children.