Yonker 2020.

Study characteristics
Patient Sampling	Purpose: diagnosis of SARS‐CoV‐2 infection (mild COVID‐19 disease) in children; to describe the paediatric impact of COVID‐19, specifically focusing on viral burden, susceptibility to disease and immune responses Design: cross‐sectional cohort study, retrospective data collection Recruitment: paediatric patients ≤ 22 years of age presenting to Infection Control clinics for medical evaluation of symptoms concerning for COVID‐19 or admitted for acute symptoms related to COVID‐19 or multisystem inflammatory syndrome in children (MIS‐C) were offered enrolment in the paediatric COVID‐19 bio repository Sample size: n = 174 (49 cases), excluding 18 MIS‐C patients Inclusion criteria: children ages 0‐22 years; symptoms concerning for COVID‐19 or admitted for acute symptoms related to COVID‐19 or MIS‐C; informed consent, and if appropriate, assent,were verbally obtained by the patients or parent/guardian Exclusion criteria: none specified
Patient characteristics and setting	Facility cases: positive RT‐PCR for SARS‐CoV‐2 Facility controls: negative RT‐PCR for SARS‐CoV‐2 Country: Massachusetts, USA Dates: not stated (before 29 July 2020 (date of article submission)) Symptoms and severity: asymptomatic to mild symptoms to MIS‐C Demographics: mean age: cases 12.7 years, controls 9.6 years M%/F%: cases 46.9/53.1, overall 53.6/46.4 Exposure history: household exposures cases: mother: 40.8%, father: 26.5%, sibling: 18.4%, other: 18.4%, no household exposure: 18.4% Household exposures controls: mother: 16.8%, father: 8.8%, sibling: 6.4%, other: 15.2%, no household exposure: 56.0%
Index tests	Nasal congestion Rhinorrhea Anosmia or hyposmia Headache Myalgia or arthralgia Sore throat Cough Fever Rash Nausea or vomiting Diarrhoea Anorexia Chills Dyspnoea Fatigue Dysgeusia Altered mental status Lymphadenopathy
Target condition and reference standard(s)	TC: SARS‐CoV‐2 infection RS: SARS‐CoV‐2 RT‐PCR test (nasopharyngeal or oropharyngeal swabs)
Flow and timing	Index tests and reference standard both taken at presentation
Comparative
Notes	MIS‐C patients were excluded for our analyses Funding: Supported by the National Heart, Lung, and Blood Institute (5K08HL143183 to L.Y.), the Cystic Fibrosis Foundation (YONKER18Q0 to L.Y.), the National Institute of Child Health and Human Development (K08 HD094638 [to A.N.] and R01HD100022 [to A.E.]), Mark and Lisa Schwartz (to J.L.), the National Institute of Diabetes and Digestive and Kidney Diseases (DK039773, DK072381 [to J.B.] and DK104344 [to A.F.]), the National Institute of Allergy and Infectious Disease (K24AI141036 to I.B.), the Centers for Disease Control and Prevention (U01CK000490 to E.R.), and the Department of Pediatrics and the Department of Obstetrics/Gynecology at Massachusetts General Hospital (to L.Y. and A.E.)
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Yes
Did the study avoid inappropriate inclusions?	Yes
Could the selection of patients have introduced bias?		Low risk
Are there concerns that the included patients and setting do not match the review question?			Low concern
DOMAIN 2: Index Test (All tests)
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	No
Could the conduct or interpretation of the index test have introduced bias?		High risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
Could the reference standard, its conduct, or its interpretation have introduced bias?		Low risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			Low concern
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Could the patient flow have introduced bias?		Low risk