ObjectivesAntigen tests have recently emerged as an interesting alternative to SARS-CoV-2 diagnostic PCR, thought to be valuable especially for the screening of bigger communities. To check appropriateness of the antigen based testing, we determined sensitivity of two point-of-care antigen tests when applied to a cohort of COVID-19 symptomatic, COVID-19 asymptomatic and healthy persons.MethodsWe examined nasopharyngeal swabs with antigen test 1 (Panbio Covid-19 Ag Rapid Test, Abbott) and antigen test 2 (Standard F Covid-19 Ag FIA, SD Biosensor). An additional nasopharyngeal and oropharyngeal swab of the same individual was checked with PCR (Allplex SARS-nCoV-2, Seegene). Within a 4-day period in October 2020, we collected specimens from 591 subjects. Of them, 290 had COVID-19 associated symptoms.ResultsWhile PCR positivity was detected in 223 cases, antigen test 1 and antigen test 2 were found positive in 148 (sensitivity 0.664, 95% CI 0.599 - 0.722) and 141 (sensitivity 0.623, 95% CI 0.558 - 0.684) patients, respectively. When only symptomatic patients were analysed, sensitivity increased to 0.738 (95% CI 0.667 - 0.799) for the antigen test 1 and to 0.685 (95% CI 0.611 - 0.750) for the antigen test 2. The substantial drop in sensitivity to 12.9% (95% CI 0.067 - 0.234) was observed for samples with the PCR threshold cycle above > 30.ConclusionsLow sensitivity of antigen tests leads to the considerable risk of false negativity. It is advisable to implement repeated testing with high enough frequency if the antigen test is used as a frontline screening tool.
Background The rapid diagnostics tests for SARS‐CoV‐2 antigen vary in their sensitivities, and moreover, genomic mutations may further affect the performance of the assays. We aimed to evaluate the analytical performance of an automated antigen assay and compare its sensitivity in Delta‐ and Omicron‐variant positive clinical samples. Material and methods The analytical performance of an automated mariPOC SARS‐CoV‐2 antigen test was evaluated on a population of community‐dwelling subjects with mild respiratory symptoms or being asymptomatic investigated by the RT‐qPCR Allplex™ SARS‐CoV‐2 assay. The sensitivity and specificity of the antigen test were evaluated on prospective 621 nasopharyngeal swabs along with oropharyngeal swabs. The sensitivity regarding variants determined by the Allplex™ SARS‐CoV‐2 Variant assays was analysed in additional, retrospective 158 Delta and 59 Omicron samples. Results The overall sensitivity of the antigen test in prospective samples was 77.9% (113/145; 95% confidence interval [CI] 70.3–84.4) with the specificity of 99.8% (95% CI 98.8–100). Regarding the variant, the sensitivity was higher in Omicron‐variant samples, 93.2% (55/59; 95% CI 83.5–98.1), compared to Delta‐variant samples, 71.5% (113/158; 95% CI 63.8–78.4; p = .001). Conclusion In community‐dwelling subjects with mild respiratory symptoms or being asymptomatic, the automated mariPOC SARS‐CoV‐2 antigen test showed high sensitivity over 98.0% in subgroup samples with cycle threshold (Ct) values < 25. Regarding the variant, the antigen test sensitivity was higher in the Omicron‐variant samples compared to the Delta‐variant samples. The analytical performance of the antigen test can differ between the SARS‐CoV‐2 variants, and a re‐evaluation should be performed for new circulating lineages.
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