Field evaluation of COVID‐19 antigen tests versus RNA based detection: Potential lower sensitivity compensated by immediate results, technical simplicity, and low cost

Abstract

One year into the coronavirus disease 2019 (COVID-19) pandemic, diagnostic strategies, although central for contact tracing and other preventive measures, are still limited. To meet the global demand, lower cost and faster antigen tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection are a convenient alternative to the gold standard reverse transcription-polymerase chain reaction (RT-PCR) assay. We tested laboratory-based RT-PCR RNA detection and two rapid antigen detection (RAD) tests, based on the immunochromatography test for nucleocapsid protein of SARS-CoV-2 (COVID-19 Ag ECO Test, ECO Diagnóstica, and Panbio COVID-19 Ag Rapid Test Abbott). Paired collection and testing were done in a small prospective open study in three clinical services in São Paulo, constituted of mostly symptomatic volunteers at collection (97%, 109/112) for amedian of 4 days (interquartile range: 3-6), ranging from 1 to 30. Among the 108 paired RT-PCR/RAD tests, results were concordant in 96.4% (101/108). The test's performance was comparable, with an overall sensitivity of 87% and a specificity of 96%. These observations add to other data that suggest that antigen tests may provide reasonable sensitivity and specificity and deserve a role to improve testing strategies, especially in resource-limited settings.

Analytical Performances of the Point-of-Care BIOSYNEX COVID-19 Ag BSS for the Detection of SARS‐CoV‐2 Nucleocapsid Protein in Nasopharyngeal Swabs: A Prospective Field Evaluation During the COVID-19 Third Wave in France

“…Finally, the Ag-RDT RDT BIOSYNEX COVID-19 Ag BSS ful lled the current WHO's recommendations for a screening Ag-RTD stating that, at minimum, Ag-RDTs would need to correctly identify signi cantly more cases than they would miss (sensitivity ≥ 80%) and would have very high speci city (≥ 97-100%) [20]. Furthermore, analytical performances of comparable order as those of our study Ag-RDT were previously reported for some Ag-RDTs in lateral ow immunoassay format [7,9,21,[25][26][27][28][29][30][31][32][33][34][35], while several studies have reported much lower sensitivity levels contrasting with always high speci city [3,[36][37][38][39][40][41]. For example, a comparable Ag-RDT such as the novel COVID-VIRO® from AAZ (Boulogne Billancourt, France) showed a sensitivity of 96.7% and a speci city of 100% in a real-life community setting [31].…”

Rapid antigen detection alone may not be sufficient for early diagnosis and/or mass screening of COVID‐19

“…One rapid antigen test (COVID‐VIRO®) showed an excellent sensitivity of >90% even for the samples with a low viral load (>32 C t values in RT‐qPCR), 3 one (COVID‐19 Ag ECO Test) had an overall sensitivity of 82.0%, 4 and one (Panbio™ COVID‐19 Ag Rapid Test) showed variable sensitivities (75.0%–100%) in three different investigations. 4 , 5 , 6 After excluding one study with very small samples size (n=44) that showed very high sensitivity (100%), 4 we recalculated the sensitivity of the Panbio™ Ag Test using the data from two different investigations, 5 , 6 and obtained a 76.3% (216/283) (Table 1 ). In spite of having a significantly positive correlation of antigen testing with SARS‐CoV‐2 viral culture assays, 10 it is clear that the vast majority (6/7) of tested rapid antigen assays have substantially lower sensitivity than the WHO recommended standard, especially for asymptomatic cases.…”

Review on oxidative stress relation on COVID-19: Biomolecular and bioanalytical approach

“…One of the standardized laboratory/clinical protocols for COVID-19 is now performed on the basis of the accessibility of the complete genome of the virus [112] , which includes real-time RT-PCR assays, which uses the RNA-dependent RNA polymerase (RdRp), envelope, and nucleocapsid genes of COVID-19. Between these classifications, the RdRp assay presented the maximum analytical sensitivity, copies of RNA with reactivity that makes the detection process work correctly with high probability (95%), in which the first probe was a “pan Sarbeco-Probe” which would detect COVID 19, SARS-CoV, bat-SARS-related coronaviruses [13] , [18] , [69] , [113] . These successful reported assays had been employed in more than thirty laboratories in Europe.…”

“…As the first line is covered by the fluid, the gold nanoparticle-antibody conjugates bind to the antigens and the complicated streams together over the membrane. Reaching to the second line would be synchronizing with immobilization of the complex that captures the antibodies (if existed) and a red or blue line would show up [113] . It should be noted that individual gold nanoparticles present red color but this color of solution would change to blue in the presence of clustered gold nanoparticles in the same solution.…”