Pokorska‐Śpiewak 2021.

Study characteristics
Patient Sampling	Purpose: diagnosis of SARS‐CoV‐2 infection (mild COVID‐19 disease); to compare clinical severity and epidemiological spectrum between COVID‐19 and influenza in children Design: cross‐sectional cohort study, prospective data collection Recruitment: all consecutive paediatric patients referred to a tertiary healthcare department Sample size: n = 319 (15 cases) Inclusion criteria: clinical symptoms (WHO definition) of the disease or positive epidemiological history (international travel or contact with infected person) Exclusion criteria: not specified
Patient characteristics and setting	Facility cases: positive RT‐PCR test for SARS‐CoV‐2 Facility controls: negative RT‐PCR test for SARS‐CoV‐2 Country: Poland Dates: 01 February 2020‐15 April 2020 Symptoms and severity: mild to moderate severity, hospitalisation needed in 73% of cases and 37% of controls, none needed mechanical ventilation Demographics: age: controls median 84 months, cases median 128 months M%/F%: cases 53.3/46.7, controls 50.7/49.3 Exposure history: household contacts with confirmed positive patient: 100% of cases, 9.2% of controls; history of travel: 6.7% of cases, 25.3% of controls
Index tests	Fever Cough Shortness of breath Diarrhoea Vomiting Rhinitis Abdominal pain Sore throat Headache Myalgia Chest pain Fatigue Conjunctivitis Skin rash
Target condition and reference standard(s)	TC: SARS‐CoV‐2 infection RS: RT‐PCR (nasopharyngeal 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?	Yes
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Unclear
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?	Unclear
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