The use of denaturing solution as collection and transport media to improve SARS-CoV-2 RNA detection and reduce infection of laboratory personnel

Abstract

Accurate testing to detect SARS-CoV-2 RNA is key to counteract the virus spread. Nonetheless, the number of diagnostic laboratories able to perform qPCR tests is limited, particularly in developing countries. We describe the use of a virus-inactivating, denaturing solution (DS) to decrease virus infectivity in clinical specimens without affecting RNA integrity. Swab samples were collected from infected patients and from laboratory personnel using a commercially available viral transport solution and the in-house DS. Samples were tested by RT-qPCR, and exposure to infective viruses was also accessed by ELISA. The DS used did not interfere with viral genome detection and was able to maintain RNA integrity for up to 16 days at room temperature. Furthermore, virus loaded onto DS were inactivated, as attested by attempts to grow SARS-CoV-2 in cell monolayers after DS desalt filtration to remove toxic residues. The DS described here provides a strategy to maintain diagnostic accuracy and protects diagnostic laboratory personnel from accidental infection, as it has helped to protect our lab crew.

Keywords: COVID-19 diagnostics; Laboratory personnel; RNA integrity; SARS-CoV-2; Sampling solution.

Fig. 1

Comparative analysis of RNAse P mRNA amplification in samples extracted from VTM and DS. C_T obtained for the RNAse P mRNA from samples A, B, C, and D, stored and extracted from VTM (virus transport media) or DS (denaturing solution)

Fig. 2

RNA viability in DS solution after storage at 4 °C and room temperature for 16 days. DS tubes were spiked with SARS-CoV-2 RNA and stored under refrigeration or at room temperature. The presence of SARS-CoV-2 RNA was detected by RT-PCR (N1 and N2 viral gene probes) in the samples after 1, 2, 4, 8, and 16 days of storage

Fig. 3

Comparative analysis of viral genes and RNAse P mRNA amplification in clinical samples extracted from VTM or DS. Mean C_T of positive and negative samples for N1, N2, and N3 viral genes, extracted from VTM and DS (n = 6). VTM+: positive samples with viral transport media, DS+: positive samples with denaturing solution, VTM−: negative samples with viral transport media, DS−: negative samples with denaturing solution. Data were compared using a two-way analysis of variance (ANOVA). **P < 0.05 when comparing the groups VTM− and DS−