Zurl 2021.

Study characteristics
Patient Sampling	Purpose: diagnosis of SARS‐CoV‐2 infection (mild COVID‐19 disease); to analyse the infection rate in symptomatic children Design: cross‐sectional cohort, retrospective data collection Recruitment: children presenting at university hospital's children's ED Sample size: n = 1105 (10 cases) Inclusion criteria: children with symptoms and anamnestic details according to national criteria for suspicion of SARS‐CoV‐2, and no alternative diagnosis Exclusion criteria: not specified
Patient characteristics and setting	Facility cases: SARS‐CoV‐2 PCR test‐positive Facility controls: SARS‐CoV‐2 PCR test‐negative Country: Austria Dates: 19 March 2020‐15 August 2020 Symptoms and severity: not specified, mostly mild to moderate severity, 50% of cases requiring hospital admission, 32.4% of controls Demographics: median age: cases: 8.4 years, controls: 3.2 years gender M%/F%: cases 50/50, controls 52.1/47.9 Exposure history: known contact with a case: cases 0%; controls 1.4%
Index tests	Sore throat Respiratory signs and symptoms (all) laryngitis/hoarseness/stridor cough bronchitis/rhonchi dyspnoea/shortness of breath tachypnoea (age adapted) Temperature ≥ 37.5 °C temperature ≥ 37.5 °C reported prior to admission temperature ≥ 37.5 °C measured at admission Sudden onset of anosmia and or a‐/‐dysgeusia
Target condition and reference standard(s)	TC: SARS‐CoV‐2 infection RS: PCR for SARS‐CoV‐2 (naso‐ or oropharyngeal swabs)
Flow and timing	Timing not specified
Comparative
Notes	Funding: none declared
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	No
Did the study avoid inappropriate inclusions?	Yes
Could the selection of patients have introduced bias?		High 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?	Unclear
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Could the patient flow have introduced bias?		Unclear risk

BP: blood pressure; CDC: Centre for Disease Control; COPD: constructive obstructive pulmonary disease; COVID‐19: coronavirus disease 2019; CT: computed tomography; ED: emergency department; ENT: ear, nose and throat; F: female; FiO₂: fraction of inspired oxygen; GI: gastrointestinal; GP: general practitioner; HCW: healthcare workers; ICU: intensive care unit; IgM: immunoglobulin M; IQR: interquartile range; M: male; NCP: novel coronavirus pneumonia; OTD: olfactory and taste disorder; PaO₂: partial pressure of oxygen; POC: point‐of‐care; RS: reference standard; RT‐PCR: reverse transcription polymerase chain reaction; SARS‐CoV‐2: severe acute respiratory syndrome coronavirus 2; SD: standard deviation; SpO₂: oxygen saturation; TC: target condition; WBC: blood white blood cell; WHO: World Health Organization; 2019‐nCoV: 2019 novel coronavirus