Table 2.
Characteristics of the studies’ index test and reference standard. (created by the authors)
| Study identifier | Index test | Reference standard | ||||||
| Name (manufacturer) | Test method*/readout* | Target analyte* | Specimen type used in study | RT-PCR assay | Viral target | Positivity threshold | Specimen type used in study | |
| Akingba | Panbio COVID-19 Ag Rapid Test (Abbott) | LFA/visual | N protein | NP | Seegene nCoV assay | Three targets (not specified) | At least one target Ct value <38; inconclusive: two targets negative and one target positive with Ct value≥38 |
NP (same swab used for antigen test) |
| Bianco | LumiraDx SARS-CoV-2 Ag Test (LumiraDx) | Microfluidic FIA/automated | N protein | Nasal | XpertXpress SARS-CoV-2 assay (Cepheid)† | nr | nr | NP |
| Dřevinek | 1: Panbio COVID-19 Ag Rapid Test (Abbott) 2: Standard F COVID-19 FIA Ag (SD Biosensor) |
1: LFA/visual 2: FIA/automated |
1: N protein 2: N protein |
1: NP 2: NP |
Allplex SARS-nCoV-2 (Seegene) | N, E and RdRP/S genes | At least one target with Ct value≤40 | NP+OP |
| González-Donapetry | Panbio COVID-19 Ag Rapid Test (Abbott) | LFA/visual | N protein | NP | Vircell SARS-CoV-2 real-time PCR kit (Vircell) | N and E gene | Both targets with Ct value≤40 | NP |
| Homza | ECOTEST COVID-19 Antigen Rapid Test (Assure Tech) | LFA/visual | N protein | NP (nostril 1) | COVID-19 Multiplex RT-PCR Kit (Diana Biotechnologies) | S gene and gene coding the EndoRNAse | nr | NP (nostril 2) |
| Kiyasu | QuickNavi COVID-19 Ag (Denka) | LFA/visual | N protein | NP | RT-PCR (National Institute of Infectious Diseases, Japan)‡ | nr | nr | NP |
| L’Huillier | Panbio COVID-19 Ag Rapid Test (Abbott) | LFA/visual | N protein | NP | 1: Cobas SARS-CoV-2 assay (Roche) or 2: Nimbus RT-PCR assay | 1: nr 2: nr |
1: unclear 2: unclear |
NP |
| Möckel | Roche SARS-CoV-2 Rapid Antigen Test (SD Biosensors) | LFA/visual | N protein | ONP | 1: Cobas SARS-CoV-2 assay (Roche) or 2: SARS-CoV-2 E-gene assay (TibMolbiol) | 1: nr 2: E gene |
1: unclear 2: unclear |
ONP |
| Pilarowski | BinaxNOW COVID-19 Ag Card (Abbott) | LFA/visual | N protein | AN (bilateral) | RenegadeXP§ (RenegadeBio) | N gene | ‘No Ct cut-off’, Ct cut-off value=30 and 35 | AN (bilateral) |
| Pollock a | BinaxNOW COVID-19 Ag Card (Abbott) | LFA/visual | N protein | AN (bilateral) | CRSP SARS-CoV-2 Real-time RT-PCR Diagnostic Assay (MIT/Harvard) | N2 gene | Ct cut-off value=40 (in addition: 25, 30, 35) | AN (bilateral) |
| Pollock b | CareStart COVID-19 Antigen test (Access Bio) | LFA/visual | N protein | AN (bilateral) | CRSP SARS-CoV-2 Real-time RT-PCR Diagnostic Assay (MIT/Harvard) | N2 gene | Ct cut-off value=40 (in addition: 25, 30, 35) | AN (bilateral) |
| Prince-Guerra | BinaxNOW COVID-19 Ag Card (Abbott) | LFA/visual | N protein | AN (bilateral) | 1: CDC 2019-nCoV Real-time RT-PCR Diagnostic Panel or 2: Fosun COVID-19 RT-PCR Detection Kit | 1: nr 2: nr |
1: nr 2: nr |
NP (bilateral) |
| Shah | BinaxNOW COVID-19 Ag Card (Abbott) | LFA/visual | N protein | AN (nostril 1) | TaqPath SARS-CoV-2 Combo Kit (Thermo Fisher Scientific) | S, N and Orf1Ab genes | Ct value≤37 for at least two targets; inconclusive: one target positive | AN (nostril 2) |
| Sood | BinaxNOW COVID-19 Ag Card (Abbott) | LFA/visual | N protein | AN | Curative SARS-Cov-2 Assay (EUA for testing at KorvaLabs) | nr | Ct value≤40 | Oral fluid¶ |
| Takeuchi | QuickNavi COVID-19 Ag (Denka) | LFA/visual | N protein | NP | RT-PCR (National Institute of Infectious Diseases, Japan)** | nr | nr | NP |
| Torres | Panbio COVID-19 Ag Rapid Test (Abbott) | LFA/visual | N protein | NP (left nostril) | TaqPath SARS-CoV-2 Combo Kit (Thermo Fisher Scientific) | N gene | Ct value≤35 (in addition: ≤30, ≤25, ≤20) | NP (right nostril) |
| Villaverde | Panbio COVID-19 Ag Rapid Test (Abbott) | LFA/visual | N protein | NP | RT-PCR (not further specified) | E and RdRp genes | nr | NP |
*Technical specification taken from FIND Test Directory/manufacturer’s instructions for use if not reported in paper.
†XpertXpress SARS-CoV-2 assay has FDA EUA for both point-of-care and laboratory use (https://www.fda.gov/media/136316/download—accessed online: 20 June 2021). The authors reported that RT-PCR was performed ‘at the Microbiology and Virology unit’ of the ‘University Hospital Citta della Salute e della Scienza di Torino, Turin (Italy)’ which is, according to the authors, the ‘largest tertiary care facility in Europe’,37 therefore we considered the reference standard as eligible.
‡Classified as ‘reference real-time RT-PCR’ which was performed at the manufacturer’s site. RT-PCR was performed in an in-house microbiology laboratory. In case of discordant RT-PCR test results, a re-evaluation was performed ‘with a published for SARS-CoV-2’54. The final decision was based on the result of the latter RT-PCR test.
§PCR-positive results were confirmed by the "standard US Centers for Disease Control and Prevention methodology using Qiagen viral RNA purification kits and singleplex RT-PCR detection of the nucleoprotein gene".27
¶The FDA’s Accelerated Emergency Use Authorisation (EUA) Summary (https://www.fda.gov/media/137089/download—accessed online: 30 May 2021) states that the ‘collection of … oral fluid specimens is limited to symptomatic individuals within 14 days of COVID-19 symptom onset … Negative results for SARS-CoV-2 RNA from oral fluid specimens should be confirmed by testing of another specimen type authorised for use with this test if clinically indicated’.
**Classified as ‘reference real-time RT-PCR’50 which was performed at the manufacturer’s site. RT-PCR was performed in an in-house microbiology laboratory. In case of discordant PCR test results, a re-evaluation was performed using a BioFire Respiratory Panel 2.1 on the BioFire FilmArray system.
AN, anterior nasal (nares); Ct, cycle threshold; FIA, fluorescent immunoassay; LFA, lateral flow immunochromatographic assay; NP, nasopharyngeal; nr, not reported; ONP, oro-nasopharyngeal; OP, oropharyngeal; RT-PCR, reverse transcription polymerase chain reaction.