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Background: In the pandemic, testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by real-time polymerase chain reaction is one of the pillars on which countermeasures are based. Factors limiting the output of laboratories interfere with the effectiveness of public health measures. Conserving reagents by pooling samples in low-probability settings is proposed but may cause dilution and loss of sensitivity. Blood transfusion services had experience in performance of high throughput nucleic acid testing (NAT) analysis and can support the national health system by screening of the inhabitants for SARS-COV-2.
Methods: We evaluated a new approach of a multiple-swab method by simultaneously incubating multiple respiratory swabs in a single tube. Analytical sensitivity was constant up to a total number of 50 swabs. It was consequently applied in the testing of 50 symptomatic patients (5-sample pools) as well as 100 asymptomatic residents of a nursing home (10-sample pools).
Results: The novel method did not cause false-negative results with nonsignificantly differing cycle threshold values between single-swab and multiple-swab NAT. In two routine applications, all minipools containing positive patient samples were correctly identified.
Conclusions: The new method enables countries to increase the total number of testing significantly. The multiple-swab method is able to screen system relevant groups of employees frequently. The example in Germany shows that blood transfusion services can support general health systems with their experience in NAT and their high-throughput instruments. Screening of a huge number of inhabitants is currently the only option to prevent a second infection wave and enable exit strategies in many countries.
Background In the pandemic, testing for SARS-CoV-2 by RT-PCR in one of the pillars on which countermeasures are based. Factors limiting the output of laboratories interfere with the effectiveness of public health measures. Conserving reagents by pooling samples in low-probability settings is proposed, but may cause dilution and loss of sensitivity.
Methods We tested an alternate approach (FACT) by simultaneously incubating multiple respiratory swabs in a single tube. This protocol was evaluated by serial incubation of a respiratory swab in up to 10 tubes. The analytics validity of this concept was demonstrated in a five-sample mini pool set-up. It was consequently applied in the testing of 50 symptomatic patients (five-sample pools) as well as 100 asymptomatic residents of a nursing home (ten-sample pools).
Results Serial incubation of a respiratory swab in up to 10 tubes did not lead to a significant decline in viral concentration. The novel FACT-protocol did not cause a false negative result in a five-sample mini-pool setup, with non-significantly differing Ct values between single sample and mini-pool NAT. In two routine applications, all mini pools containing positive patient samples were correctly identified.
Conclusions Our proposed FACT-protocol did not cause a significant loss in analytic or diagnostic sensitivity compared to single sample testing in multiple setups. It reduced the amount of reagents needed by up to 40%, and also reduced hands-on time. This method could enhance testing efficiency, especially in groups with a low pretest-probability, such as systemically relevant professional groups.