Simple and low-cost nucleic acid extraction methods for detection of SARS-CoV2 in self-collected saliva and dry oral swabs

Background: Ongoing need of alternative strategies for SARS-CoV-2 detection is undeniable. Self-collected samples without viral transport media (VTM), coupled with simple nucleic acid extraction methods for SARS-CoV-2 PCR are beneficial.

Objectives: To evaluate results of SARS-CoV-2 PCR using simple nucleic acid extraction methods from self -collected saliva and oral swabs without VTM.

Methods: A cross-sectional single-centre study was conducted on 125 participants (101 SARS-CoV-2 positive cases and 24 controls). PCR was performed following five simple nucleic acid extraction methods on self -collect saliva and oral swabs without VTM and results were compared with gold standard PCR. For saliva, kit-based extraction (SKE), Proteinase K and Heat extraction (SPHE), only Heat extraction (SHE) methods and for dry oral swabs, Proteinase K and Heat extraction (DPHE) and only Heat extraction (DHE) was performed.

Results: SARS-CoV-2 was detected in self-collected saliva and oral swabs. 93.07% were correctly classified as positive by SKE, 69.31% by SHE, 67.33% by SPHE, 67.33% by DPHE and 55.45% by DHE. Discriminant power of SKE was significantly higher than other methods (p-value < 0.001) with good- fair agreement of alternate extraction methods against gold standard.

Conclusion: Combination of self-collected saliva/ oral-swab without VTM and alternative RNA extraction methods offer a simplified, economical substitute strategy for SARS-CoV-2 detection.