Table 1.

MIS-C, PIMS-TS, and MIS-A case definitions

	CDC MIS-C case definition [5]	WHO MIS-C case definition [6]	RCPCH PIMS-TS case definition [7]		CDC MIS-A case definition [8]
Age	< 21 years old	0–19 years old	Child (unspecified age)	Patient demographics	≥ 21 years old + hospitalized for ≥ 24 h OR with illness resulting in death
Fever	Fever ≥ 38.5 °C (or subjective fever) for ≥ 24 h	Fever ≥ 3 days (unspecified degree)	Persistent fever (unspecified degree)	Fever	Subjective or documented fever ≥ 38.5 °C for ≥ 24 h prior to and/or within the first 3 days of hospitalization
Inflammation	Laboratory evidence of inflammation - One or more of the following: elevated CRP, ESR, fibrinogen, procalcitonin, d-dimer, ferritin, LDH, or IL-6, elevated neutrophils, reduced lymphocytes, and low albumin	Elevated markers of inflammation - ESR, CRP, procalcitonin	Inflammation - neutrophilia, elevated CRP, and lymphopenia	Requires 3 of the following clinical criteria (one must be a primary clinical criterion), evidence of inflammation, and SARS-CoV-2 infection:
System involvement	Clinically severe illness requiring hospitalization with ≥ 2 organ systems involved	Two of the following: - Rash or bilateral conjunctivitis or mucocutaneous inflammation - Hypotension or shock - Features of myocardial dysfunction, pericarditis, valvulitis, or coronary abnormalities via echocardiography findings or elevated cardiac enzymes - Evidence of coagulopathy by PT, PTT, elevated d-dimers - Acute gastrointestinal problems—diarrhea, vomiting, abdominal pain	Single or multi-organ dysfunction: - Shock, cardiac, respiratory, renal, gastrointestinal, or neurological disorder - May include children fulfilling full or partial KD criteria - “Additional features”—broad list of symptoms, lab findings, and imaging in appendix of criteria	Primary criteria	- Severe cardiac illness: myocarditis, pericarditis, coronary artery changes, or new-onset RV/LV dysfunction, 2nd/3rd degree AV block, or ventricular tachycardia - Rash and non-purulent conjunctivitis
Rule-out of additional causes	No alternative plausible diagnosis	No other obvious microbial cause of inflammation - Rule-out bacterial sepsis, staph, or strep shock syndromes	Exclusion of other microbial causes - Bacterial sepsis, staph/strep shock syndromes, viral myocarditis-related infections	Secondary criteria	- New-onset neurologic signs or symptoms: encephalopathy, seizures, meningeal signs, peripheral neuropathy - Shock or hypotension - Abdominal pain, vomiting, or diarrhea - Platelet count < 150,000/microliter
COVID-19 link	Current or recent SARS-CoV-2 infection by RT-PCR, serology, or antigen test; or exposure to suspected or confirmed COVID-19 case within 4 weeks	Evidence of COVID-19 (RT-PCR, antigen test, serology positive), or likely contact with COVID-19 patient	Positive or negative SARS-CoV-2 PCR testing	Laboratory evidence	- Elevation of two of the following: CRP, ferritin, ESR, IL-6 level, and procalcitonin - Positive SARS-CoV-2 test via RT-PCR, serology, or antigen

RT-PCR, reverse transcription-polymerase chain reaction; PT, pro-thrombin time; PTT, partial thromboplastin time; ESR, erythrocyte sedimentation rate; CRP, c-reactive protein; IL-6, interleukin-6; RV, right ventricle; LV, left ventricle; AV, atrioventricular