Table 1.

Case definitions of multisystem inflammatory syndrome in children.

Proposed organization	U.S. CDC	WHO
Age	≤20 years	≤19 years
Fever	≥38°C or subjective fever for ≥24 h	≥3 days
Laboratory evidence of inflammation	Such as elevated ESR, CRP, fibrinogen, procalcitonin, d-dimer, ferritin, LDH, IL-6, neutrophil; reduced lymphocytes, low albumin	Such as elevated ESR, CRP, procalcitonin
Multisystem involvement	≥2 systems: cardiac, renal, respiratory, hematologic, gastrointestinal, dermatologic, neurological	≥2 manifestations: 1. rash, conjunctivitis, mucocutaneous signs; 2. hypotension/shock; 3. myocardial dysfunction, pericarditis, valvulitis, coronary abnormalities; 4. coagulopathy (by PT, PTT, d-dimers); 5. acute gastrointestinal problems (diarrhea, vomiting, abdominal pain)
Requiring hospitalization	Yes	No
Evidence of COVID-19	RT-PCR, antigen test, serology test, or contact with patients with COVID-19	RT-PCR, antigen test, serology test, or contact with suspected or confirmed patients with COVID-19 within 4 weeks prior to the onset of symptoms
Other plausible diagnosis	No other microbial cause of inflammation	No alternative plausible diagnosis

ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; LDH, lactic acid dehydrogenase; IL-6, interleukin-6; PT, prothrombin time; PTT, partial thromboplastin time.