Effective high-throughput RT-qPCR screening for SARS-CoV-2 infections in children (preprint)

Systematic SARS-CoV-2 testing is a valuable tool for infection control and surveillance. However, broad application of high sensitive RT-qPCR testing in children is often hampered due to unpleasant sample collection, limited RT-qPCR capacities, and high costs. Here, we developed a high-throughput approach (Lolli-Method) for sensitive SARS-CoV-2 detection in children, combining non-invasive sample collection with an RT-qPCR-pool testing strategy. SARS-CoV-2 infections were diagnosed with sensitivities of 100% and 93.9% when viral loads were >10E6 copies/ml and >10E3 copies/ml in corresponding Naso-/Oropharyngeal-swabs, respectively. For effective application of the Lolli-Method in schools and daycare facilities, SIR-modeling indicated a preferred frequency of two tests per week. The developed test strategy was implemented in 3,700 schools and 698 daycare facilities in Germany, screening over 800,000 individuals twice per week. In a period of 3 months, 6,364 pool-RT-qPCRs tested positive (0.64%) ranging from 0.05% to 2.61% per week. Notably, infections correlated with local SARS-CoV-2 incidences as well as with a school social deprivation index. Moreover, in comparison with the alpha variant, statistical modeling revealed a 31% increase for multiple (>1 child) infections per class following infections with the delta variant. We conclude that the Lolli-Method is a powerful tool for SARS-CoV-2 surveillance and infection control in schools and daycare facilities.

Safe and effective pool testing for SARS-CoV-2 detection (preprint)

Background / Objectives: The global spread of SARS-CoV-2 is a serious public health issue. Large-scale surveillance screenings are crucial but can exceed diagnostic test capacities. We set out to optimize test conditions and implemented high throughput pool testing of respiratory swabs into SARS-CoV-2 diagnostics. Study design: In preparation for pool testing, we determined the optimal pooling strategy and pool size. In addition, we measured the impact of vortexing prior to sample processing, compared pipette- and swab-pooling method as well as the sensitivity of three different PCR assays. Results: Using optimized strategies for pooling, we systematically pooled 55,690 samples in a period of 44 weeks resulting in a reduction of 47,369 PCR reactions. In a low prevalence setting, we defined a preferable pool size of ten in a two-stage hierarchical pool testing strategy. Vortexing of the swabs increased cellular yield by a factor of 2.34, and sampling at or shortly after symptom onset was associated with higher viral loads. By comparing different pooling strategies, pipette-pooling was more efficient compared to swab-pooling. Conclusions: For implementing pooling strategies into high throughput diagnostics, we recommend to apply a pipette-pooling method, using pool sizes of ten samples, performing sensitivity validation of the PCR assays used, and vortexing swabs prior to analyses. Our data shows, that pool testing for SARS-CoV-2 detection is feasible and highly effective in a low prevalence setting.