SARS-CoV-2 Antigen Rapid Detection Tests: test performance during the COVID-19 pandemic and the impact of COVID-19 vaccination (preprint)

IntroductionDuring the COVID-19 pandemic, SARS-CoV-2 antigen rapid detection tests (RDTs) emerged as point-of-care diagnostics in addition to the RT-qPCR as the gold standard for SARS-CoV-2 diagnostics. Facing the course of the COVID-19 pandemic to an endemic characterised by several SARS-CoV-2 virus variants of concern (VOC) and an increasing public COVID-19 vaccination rate the aim of the study was to investigate the long-term test performance of SARS-CoV-2 RDT in large-scale, clinical screening use during and its influencing factors, above all SARS-CoV-2 VOC and COVID-19 vaccination. MethodsIn a prospective performance assessment conducted at a single centre tertiary care hospital, RDTs from three manufacturers (NADAL(R), Panbio, MEDsan(R)) were compared to RT-qPCR among individuals aged [≥] 6 month. The evaluation involved the determination of standardised viral load from oropharyngeal swabs as well as the evaluation of their influencing factors, especially the COVID-19 vaccination, for detecting SARS-CoV-2 in a clinical point-of-care environment spanning from 12 November 2020 to 30 June 2023 among patients, staff, and visitors of the hospital. ResultsAmong the 78,798 RDT/RT-qPCR tandems analysed, 2,016 (2.6%) tandems tested positive for SARS-CoV-2, with an overall sensitivity of 34.5% (95% CI 32.4-36.6%). A logistic regression revealed that typical COVID-19 symptoms significantly declined over the course of the study and throughout the COVID-19 pandemic, and that among the vaccinated, significantly fewer presented with an infection exhibiting typical symptoms. The employed lasso regression model indicated that only higher viral load and typical COVID-19 symptoms significantly increase the likelihood of a positive RDT result in the case of a SARS-CoV-2 infection directly. ConclusionOur findings indicate that only viral load and COVID-19 symptoms directly influence RDT performance while the obtained effects of COVID-19 vaccination and Omicron VOC both reducing RDT performance were mediated by these two factors. RDTs remain an adequate diagnostic tool for detecting SARS-CoV-2 in individuals showing respiratory symptoms. RDTs show promise beyond SARS-CoV-2, proving adaptable for detecting other pathogens like Influenza and RSV, highlighting their ongoing importance in infection control and prevention efforts.

Clinical accuracy of SARS-CoV-2 rapid antigen testing in screening children and adolescents in comparison to RT-qPCR, November 2020 to September 2022 (preprint)

Background Rapid antigen detection tests (RDT) are an easily accessible, feasible, inexpensive, and point of care method in SARS-CoV-2 diagnostics - established in adults as well as in children and adolescents. Despite this, large-scale data of clinical performance in the paediatric population especially regarding the influence of SARS-CoV-2 virus variants of concern (VOC) and COVID-19 vaccination on test accuracy is rare. Methods This single centre prospective diagnostic study evaluates three RDT (NADAL(R), Panbio, MEDsan(R)) in comparison to quantitative reverse transcription polymerase chain reaction (RT-qPCR). 9,760 oropharyngeal screening samples regarding SARS-CoV-2 VOC and COVID-19 vaccination in paediatric hospitalised patients aged younger than 18 years were enrolled. Findings RDT sensitivity was 44{middle dot}7% (157/351, 95% CI 39{middle dot}6%-50{middle dot}0%) compared to the reference standard RT-qPCR, specificity 99{middle dot}8% (9,392/9,409, 95% CI 99{middle dot}7%-99{middle dot}9%). Most SARS-CoV-2 infections considered were caused by Omicron VOC. Diagnostic accuracy of RDT depended on specimen containing viral load with a decreasing RDT sensitivity by descending viral load, corresponding with a significantly impaired sensitivity in asymptomatic children. A sensitivity of 71{middle dot}0% was obtained for a viral load higher than 106 SARS-CoV-2 RNA copies per ml suggested as infectivity threshold. No significant differences in RDT sensitivity could be observed regarding gender, symptoms, COVID-19 vaccination status, and VOC. Interpretation In a paediatric population, RDT have proven to reliably detect potentially highly infectious patients with a viral load of at least 106 SARS-CoV-2 RNA copies per ml. Due to the low sensitivity in asymptomatic individuals, the usefulness of RDT seems limited in large scale SARS-CoV-2 screening programs. Funding Federal Ministry for Education and Science (BMBF), Free State of Bavaria