ABSTRACT
Background: Antigen tests for SARS-CoV-2 testing are rapid and inexpensive but usually have lower sensitivity than RT-qPCR and are only validated for nasopharyngeal/throat swabs;the latter are considered the gold standard in terms of material collection but are not tolerated by patients with frequent sampling. The present study, therefore, investigates the extent to which SARS-CoV-2 antigen testing is comparable to RT-qPCR from an easily obtained gargle solution compared to nasopharyngeal swabs. Methods: The performance of a high-quality POC fluorescence immune antigen test in single nasal swab samples and gargle samples compared to RT-qPCR was investigated (total n = 620 samples (gargle samples = 309, and nasal swabs = 311)). Findings: In our setting, the detection of SARS-CoV2 with an antigen test was reliable up to a Ct value of 30 for single nasal swab samples and was reduced to Ct:20 for single gargle samples. The overall antigen-test sensitivity is 83.92% (swab samples) and 75.72% (gargle samples). Interpretation: Antigen tests showed reliable results up to a detection limit of Ct: 30 with only nasal swab samples but not gargle samples. If the use of gargle samples is preferred due to their advantages, such as painless testing, easy handling, and the lack of a need to involve trained personnel for sample taking, reliable results can only be achieved with RT-qPCR.
ABSTRACT
Background: Opening schools and keeping children safe from SARS-CoV-2 infections at the same time is urgently needed to protect children from direct and indirect consequences of the COVID-19 pandemic. To achieve this goal, a safe, efficient, and cost-effective SARS-CoV-2 testing system for schools in addition to standard hygiene measures is necessary. Methods: We implemented the screening WICOVIR concept for schools in the southeast of Germany, which is based on gargling at home, pooling of samples in schools, and assessment of SARS-CoV-2 by pool rRT-PCR, performed decentralized in numerous participating laboratories. Depooling was performed if pools were positive, and results were transmitted with software specifically developed for the project within a day. Here, we report the results after the first 13 weeks in the project. Findings: We developed and implemented the proof-of-concept test system within a pilot phase of 7 weeks based on almost 17,000 participants. After 6 weeks in the main phase of the project, we performed >100,000 tests in total, analyzed in 7,896 pools, identifying 19 cases in >100 participating schools. On average, positive children showed an individual CT value of 31 when identified in the pools. Up to 30 samples were pooled (mean 13) in general, based on school classes and attached school staff. All three participating laboratories detected positive samples reliably with their previously established rRT-PCR standard protocols. When self-administered antigen tests were performed concomitantly in positive cases, only one of these eight tests was positive, and when antigen tests performed after positive pool rRT-PCR results were already known were included, 3 out of 11 truly positive tests were also identified by antigen testing. After 3 weeks of repetitive WICOVIR testing twice weekly, the detection rate of positive children in that cohort decreased significantly from 0.042 to 0.012 (p = 0.008). Interpretation: Repeated gargle pool rRT-PCR testing can be implemented quickly in schools. It is an effective, valid, and well-received test system for schools, superior to antigen tests in sensitivity, acceptance, and costs.