2. Study characteristics (cross‐sectional prospective studies only).

Study ID	Target condition	Sample size	Prevalence	Country	Setting	Population	Reference standard
Alizadehsani 2021	COVID‐19 pneumonia	319	39%	Iran	ED	All patients referred to the imaging department on suspicion of COVID‐19 (with flu‐like symptoms)	Thin‐slice high‐resolution multi‐slice spiral CT scan in a supine position, and high‐resolution CT images
Bhattacharya 2021	COVID‐19	378	33%	India	ED	Patients who were suspected of COVID‐19. From 1066 suspected patients who were tested during this period, 384 patients were enrolled in the study based on the availability of informed consent and successful telephonic communication. Suspicion based on the testing advisory developed by the Indian Council of Medical Research (ICMR), Version 5, dated May 18, 2020. "ILI symptoms", defined as acute respiratory infection with fever ≥ 38 °C AND cough	RT‐PCR for SARS‐CoV‐2 (nasal + throat swab)
Bouzid 2020	COVID‐19	596	45%	France	ED	All consecutive patients presenting with an influenza‐like illness (ILI: fever with a temperature > 38.5°C, malaise, headache, and myalgia; and 1 respiratory symptom (cough, sore throat, and dyspnoea)) and admitted to the hospital through the ED	Either with QIAstat‐Dx Respiratory SARS‐CoV‐2 Panel or with a combination of the RT‐PCR RealStar SARS‐CoV‐2 Kit RUO and rapid multiplex PCR FilmArray RP2; specimen not specified
Brendish 2020	COVID‐19	1054	33%	UK	ED	All consecutive adults presenting with an acute respiratory illness or otherwise clinically suspected of having COVID‐19	Either laboratory RT‐PCR or MPOCT (QIAGEN) for SARS‐CoV‐2 (nasopharyngeal swab)
Buonafine 2020	COVID‐19	295	42%	Brazil	Outpatient setting	HCW with self‐reported fever or any of the following: acute respiratory symptoms (cough, nasal congestion, sore throat, shortness of breath), loss or changed sense of smell or taste, ocular symptoms, headache, arthralgia, myalgia, fatigue, diarrhoea, nausea, and vomiting	RT‐PCR for SARS‐CoV‐2 (nasopharyngeal and oropharyngeal swab)
Clemency 2020	COVID‐19	961	23%	USA	Outpatient setting	HCWs triaged by phone, tested at drive‐through site	RT‐PCR on nasopharyngeal or oropharyngeal swabs
Drager 2020	COVID‐19	2257	7%	Germany	Outpatient setting	All patients presenting themselves at the outpatient clinic: patients with symptoms (not further specified) + high‐risk contacts or returning from a high‐risk area were tested for SARS‐CoV‐2	Not specified (throat swab)
Fink 2021	COVID‐19/ COVID‐19 pneumonia	219	33%	Germany	ED	Patients who presented at ED with signs of a respiratory infection suspicious for COVID‐19 and received radiological imaging as well as RT‐PCR for SARS‐CoV‐2	RT‐PCR for SARS‐CoV‐2 (nasopharyngeal and oropharyngeal swab)
Gilbert 2020	COVID‐19	598	29%	Belgium	Outpatient setting	Suspected patients sent to testing centres close to ED	RT‐PCR on nasopharyngeal swabs
Haehner 2020	COVID‐19	500	7%	Germany	Outpatient setting	Patients presenting with symptoms of a common cold to a corona testing centre	RT‐PCR on throat swabs
Ishii 2021	COVID‐19	3540	5%	Japan	Outpatient setting	All consecutive participants who underwent drive‐through nasopharyngeal swab testing at an outpatient clinic. Reason for testing: upon request of the participant or participants who had been confirmed to have contacted COVID‐19 patients based on contact tracing. No clinical suspicion needed per se, but 54% of individuals were symptomatic, suggestive of COVID‐19	RT‐PCR, nasopharyngeal swab
Jeyashree 2021	COVID‐19	277	21%	India	Outpatient setting	All consecutive adults who visited COVID‐19 testing centres in Chennai city in Southern India	RT‐PCR, nasopharyngeal swab
Just 2020	COVID‐19	374	11%	Germany	Primary care	Convenience sample of patients who were tested in GPs' practices	RT‐PCR, samples not specified
Kalayjian 2020	COVID‐19	345	34%	USA	Outpatient setting	Clients entering the health centre (walk‐in clinic) were screened for symptoms and triaged to the COVID‐19 clinic. Testing was performed for patients with a documented or subjective fever within the past 72 h.	Labcorp’s nucleic‐acid amplification, threshold not specified, nasopharyngeal swabs
Kempker 2020	COVID‐19	283	18%	USA	Outpatient setting	HCWs with a viral‐like illness, triaged to the employee health services staff for a virtual clinical assessment and then scheduled for SARS‐CoV‐2 testing	RT‐PCR, nasopharyngeal swab
Krastinova 2020	COVID‐19	314	110	France	Outpatient setting	Symptomatic HCWs, defined as the presence of fever and/or respiratory symptoms	RT‐PCR, nasopharyngeal swabs
Leal 2020	COVID‐19	1583	28%	Brazil	Outpatient setting	Patients meeting the suspected COVID‐19 case definition (tested after initial screening questionnaire)	RT‐PCR, samples not specified
Maechler 2020	COVID‐19	4333	8%	Germany	Outpatient setting	Until 24 March 2020: symptomatic patients with high‐risk contacts or return from high‐risk area. From 24 March: also symptomatic people with risk factors and if the test capacity allowed also only symptomatic patients. Plus 2 subgroups of high‐risk patients in a nightclub and Charité employees	SARS‐CoV‐2 RT‐PCR test (combined oro‐ and nasopharyngeal swab)
Mansella 2020	COVID‐19	4815	12%	Switzerland	Outpatient setting	All patients presenting at the test centre with respiratory symptoms (such as shortness of breath), other flu‐like symptoms (fever, sore throat, cough) and self‐reported exposure to COVID‐19	RT‐PCR, 2 swabs from naso‐ and oropharyngeal sites combined into 1
Martin‐Sanz 2020	COVID‐19	355	61%	Spain	Outpatient setting	HCWs with suspicion of COVID‐19 infection. Suspicion of COVID‐19 was determined by the presence of either cough, fever (> 37.5 °C), headache, or breathlessness, regardless of contact with a COVID‐19 patient	SARS‐CoV‐2 next‐generation sequencing or real‐time (RT)‐PCR methods (nasal‐ and pharyngeal swabs)
Nazerian 2021	COVID‐19	838	23%	Italy	ED	Patients with suspected COVID‐19 were prospectively enrolled in 2 EDs	RT‐PCR, positive result within 5 days after ED presentation, or suggestive symptoms plus chest imaging (showing acute interstitial lung disease in the absence of an alternative diagnosis), or panel adjudication (for 3 cases without a positive PCR)
Olivar Lopez 2020	COVID‐19	510	15%	Mexico	ED	All patients < 18 years who presented with a clinical picture compatible with COVID‐19 (= fever, respiratory symptoms or general malaise) at the ED of a COVID paediatric reference hospital	RT‐PCR, nasopharyngeal swabs
O'Reilly 2020a	COVID‐19	240	5%	Australia	ED	Patients who meet the testing criteria for COVID‐19 and who present at the ED	RT‐PCR, sample not specified
O'Reilly 2020b	COVID‐19	1334	4%	Australia	ED	All adult patients who met criteria for "suspected COVID‐19" and underwent testing for SARS‐CoV‐2 were eligible for inclusion. Testing criteria guided by various health jurisdictions and evolved throughout the project	SARS‐CoV‐2 RT‐PCR test (nasopharyngeal swab)
Peyrony 2020	COVID‐19	391	58%	France	ED	Patients tested at ED, decision to test based on clinician’s discretion	RT‐PCR on nasal swabs
Pivetta 2020	COVID‐19	228	47%	Italy	ED	All adults (≥18 years) who screened positive for acute symptoms associated with SARS‐CoV‐2 infection at triage (= fever, dyspnoea, new or worsening cough, sore throat, diarrhoea, ageusia, anosmia and asthenia)	RT‐PCR (nasopharyngeal swabs), and in some cases other information including clinical, lab, imaging
Pokorska‐Śpiewak 2021	COVID‐19	319	5%	Poland	Mixed in/outpatient paediatric setting	All consecutive paediatric patients referred to a tertiary healthcare department (referral based on clinical symptoms (WHO definition) of the disease or positive epidemiological history (international travel or contact with infected person)	RT‐PCR (nasopharyngeal swabs)
Porto 2021	COVID‐19	1297	32%	Brazil	Outpatient setting	All patients presenting at the Piquet Carneiro Polyclinic, test indication not specified, but high proportion of symptomatic individuals in recruited population	RT‐PCR (nasopharyngeal swabs)
Romero‐Gameros 2020	COVID‐19	139	52%	Mexico	ED	Patients who sought a respiratory triage assessment at ED of tertiary care hospital due to COVID‐19 suspicion	RT‐PCR (nasopharyngeal swabs)
Romero‐Gameros 2021	COVID‐19	2137	54%	Mexico	ED	Adults > 17 years, with high clinical probability of SARS‐CoV‐2 and confirmatory RT‐PCR available	RT‐PCR (nasopharyngeal swabs)
Rutten 2020a	COVID‐19	1969	44%	The Netherlands	Nursing home	Patients with at least 2 of the following symptoms: fever/feverish feeling, cough and shortness of breath ‐ later on (from 10 April 2020) patients with atypical symptoms were added	RT‐PCR test (specimen not specified)
Rutten 2020b	COVID‐19	4007	38%	The Netherlands	Nursing home	All nursing home residents with a clinical suspicion of COVID‐19 based on the physician's assessment and for whom they had the result of the RT‐PCR	RT‐PCR test (specimen not specified)
Saegerman 2021	COVID‐19	2152	27%	Belgium	ED	All suspected patients directed to the triage centres of 2 university hospital EDs (no definition of 'suspected')	RT‐PCR test (specimen not specified)
Salmon Ceron 2020	COVID‐19	1824	47%	France	Outpatient setting	Patients suspected of SARS‐CoV‐2 infection, tested at screening centre	RT‐PCR test (nasopharyngeal swabs)
Trubiano 2020	COVID‐19	2935	4%	Australia	Outpatient setting	Patients presenting at a COVID‐19 rapid assessment screening clinic, meeting DHHS screening criteriaa	RT‐PCR test (nasopharyngeal swabs)
Tudrej 2020	COVID‐19	816	24%	France	Primary care/ outpatient setting	Patients referred by GPs for PCR testing at lab	RT‐PCR test (nasopharyngeal swabs)
Van Loon 2021	COVID‐19	373	50%	Belgium	Outpatient setting	All hospital HCWs self‐reporting mild symptoms of an acute upper or lower respiratory tract infection were tested in a large non‐academic hospital	RT‐PCR test (nasopharyngeal swab)
Van Walraven 2021	COVID‐19	9172	6%	Canada	Outpatient setting	Presence of symptoms including rhinorrhoea; fever symptoms including rigor, chills, perceived fever, or documented fever at home or at the screening clinic; cough; and shortness of breath. Any infection risk factor including close contact with a person with known or presumed COVID‐19 disease or recent travel outside of Canada. In the absence of these indications, HCWs were included if they had symptoms of sore throat, sputum production, or rhinorrhoea.	RT‐PCR test (nasopharyngeal and throat swabs)
Villerabel 2021	COVID‐19	809	7%	France	Outpatient setting	All HCWs and adult patients presenting themselves at the COVID‐19 screening facility of the university hospital of Montpellier	RT‐PCR test (nasopharyngeal swabs)
Wee 2020	COVID‐19	870	18%	Singapore	ED	Patients presenting with respiratory symptoms or travel history	RT‐PCR test (nasopharyngeal swabs)
Wernhart 2020	COVID‐19	80	6%	Germany	Primary care	All patients with respiratory symptoms reporting to 3 rural GP offices in North Rhine‐Westphalia, Germany	RT‐PCR test (nasopharyngeal swabs)
Yonker 2020	COVID‐19	174	28%	USA	Mixed in/outpatient paediatric setting	Paediatric patients ≤ 22 years of age; symptoms concerning for COVID‐19 or admitted for acute symptoms related to COVID‐19 or multisystem inflammatory syndrome in children	RT‐PCR test (nasopharyngeal or oropharyngeal swabs)
CT: computed tomography; ED: emergency department; GP: general practitioner; HCW: healthcare worker; MPOCT: molecular point‐of‐care test; RT‐PCR: reverse transcription polymerase chain reaction; WHO: World Health Organization

^aDHHS (Victorian Department of Health and Human Services) criteria for SARS‐CoV‐2 testing: fever OR chills in the absence of an alternative diagnosis that explains the clinical presentation OR acute respiratory infection symptoms (e.g. cough, sore throat, shortness of breath, runny nose, loss of smell or loss of taste)