Abstract
Rapid SARS-CoV-2 antigen tests are potentially useful tools for screening carriers with high viral load. This study was aimed to assess the potential association between viral load and positivization time of a manual SARS-CoV-2 commercial antigen test in routine nasopharyngeal specimens. In a sample of subjects undergoing routine diagnostic testing, SARS-CoV-2 positivity of nasopharyngeal samples was assayed with both molecular (Altona Diagnostics RealStar SARS-CoV-2 RT-PCR Kit) and antigenic (Roche SARS-CoV-2 Rapid Antigen Test) tests. Positivization time of rapid antigen test was correlated and compared with viral load expressed as mean of SARS-CoV2 E/S genes cycle threshold (Ct) values. The study sample consisted of 106 patients (median age 48 years, 55 women) with positive results of rapid SARS-CoV-2 antigen testing. A highly significant Spearman's correlation was found between mean SARSCoV-2 E/S genes Ct values and positivization time of manual antigen test (r= 0.70; p<0.001). The positivization time of rapid SARS-CoV-2 antigen test displayed an area under the curve of 0.82 (95%CI, 0.74-0.89) for predicting nasopharyngeal samples with high viral load (i.e., mean Ct <20). A positivization time cut-off of 32 SEC had 94.9% sensitivity and 58.2% specificity for detecting specimens with high viral load. The overall agreement between mean Ct value <20 and positivization time <32 SEC was 70.8%. Positivization time of rapid SARS-CoV-2 antigen tests may provide easy and rapid information on viral load, thus making this type of manual assay potentially suitable for quick and reliable detection and isolation of supercarriers.
Highlights
Molecular identification of severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) RNA remains the reference technique for diagnosing coronavirus disease 2019 (COVID-19) infection, the use of laboratory-based immunoassays or manual antigen tests is rapidly growing around the world [1]
Due to the immense number of diagnostics tests that are still needed within the timeframe of the ongoing COVID-19 pandemic, and due to a reliable prevision that such volume may further increase with progressive diffusion of highly mutated and more infectious lineages such as the new Omicron (B.1.1.529) variant [5], rapid antigen tests can be considered a potentially useful screening tool, especially suited for identification of individuals bearing high nasopharyngeal SARS-CoV-2 viral loads
The final study population consisted of 106 patients following the exclusion of 615 patients with negative results on the rapid antigen test, whose samples were unusable for evaluating the strength of association between viral load and positivization time
Summary
Molecular identification of severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) RNA remains the reference technique for diagnosing coronavirus disease 2019 (COVID-19) infection, the use of laboratory-based immunoassays or manual (rapid) antigen tests is rapidly growing around the world [1]. Due to the immense number of diagnostics tests that are still needed within the timeframe of the ongoing COVID-19 pandemic, and due to a reliable prevision that such volume may further increase with progressive diffusion of highly mutated and more infectious lineages such as the new Omicron (B.1.1.529) variant [5], rapid antigen tests can be considered a potentially useful screening tool, especially suited for identification of individuals bearing high nasopharyngeal SARS-CoV-2 viral loads These patients, who are conventionally called »super-carriers« and »super-spreaders«, may be responsible for a disproportionate number of secondary infections compared to an »average« infectious individual, due to the higher volume of viral particles that they could disseminate in the environment [6]. A high number and heterogeneity of interpersonal contacts, along with high viral load in the upper and/or lower respiratory tracts, are currently considered the main drivers of super-spreading events [7], such that is has been estimated that an accurate and timely identification of these super-carriers would allow prevention of up to 90% of all secondary SARS-CoV-2 infections [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
