Development and implementation of a RT-qPCR extraction-free protocol for the detection of SARS-CoV-2 and impact on the turn-around-time.

ABSTRACT

The occurrence of the COVID-19 second-wave outbreak in Europe has pushed laboratories performing molecular SARS-CoV-2 tests to increase their throughput and decrease the result rendering time. In this evaluation, we tested for the first time a new, extraction-free, protocol with the Allplex SARS-CoV-2 Assay RT-qPCR kit on a Nimbus platform. Ninety-one samples, of which 71 previously tested positive with RT-qPCR with extraction were immediately analyzed without extraction, using only a dilution and thermal shock protocol. The positive and negative percentage agreements were respectively 97.2% (95% confidence interval [CI] 0.90-0.99) and 95.0% (95% CI 0.76-0.99). The two false negatives observed were very weakly positive with the comparison method. Moderate variations in Ct of the targeted genes were observed (median ± 95% CI) E gene, +2.49 ± 0.44; N gene, +0.98 ± 0.54; RdRP/S genes, +2.64 ± 0.48. On the other hand, the number of tests performed within 24 h raised from 86.4% to 97.8%, the turn-around time decreased from 1918 to 0903 (p < .0001), and the number of tests that can be performed per day doubled since this technique was introduced routinely in our laboratory.