Abstract
Background & objectives: In the present scenario, the most common sample for diagnosis of COVID-19 by reverse transcription polymerase chain reaction (RT-PCR) is nasal and throat swab (NTS). Other sampling options such as gargle lavage have found limited application in clinical use mostly because of unavailability of an appropriate gargling liquid. This study was conducted to assess the stability of SARS-CoV-2 RNA in normal saline at 4°C that can serve as a gargling liquid as well as a transport medium. The study also looked at the agreement between NTS and gargle lavage/saliva for the detection of SARS-CoV-2.
Methods: In 29 consecutive real-time RT-PCR (rRT-PCR) positive COVID-19 patients, paired NTS, gargle and saliva samples were taken. Samples were processed by rRT-PCR for the detection of SARS-CoV-2 RNA. To assess the SARS-CoV-2 RNA stability in normal saline, gargle lavage specimens were divided into two aliquots; one subset of the specimen was run within 4-6 h along with the routine samples (NTS and saliva) and the other subset was stored at 4°C and processed after 24-30 h. Agreement between cycle threshold (Ct) values from both the runs was compared using Bland-Altman (BA) analysis.
Results: The positivity rates of rRT-PCR in NTS, saliva and gargle lavage samples were 82.7 (24/29), 79.3 (23/29) and 86.2 per cent (25/29), respectively. BA plot showed a good agreement between the Ct values of fresh and stored gargle samples, stipulating that there were no significant differences in the approximate viral load levels between the fresh and stored gargle lavage samples (bias: E gene -0.64, N gene -0.51, ORF gene -0.19).
Interpretation & conclusions: Our study results show stability of SARS-CoV-2 RNA in the gargle samples collected using normal saline up to 24-30 h. Gargle lavage and saliva specimen collection are cost-effective and acceptable methods of sampling for the detection of SARS-CoV-2 RNA by rRT-PCR. These simplified, inexpensive and acceptable methods of specimen collection would reduce the cost and workload on healthcare workers for sample collection.
Keywords: COVID-19; RNA stability; SARS-CoV-2; gargle lavage; nasal swab; saliva; throat swab.
【저자키워드】 COVID-19, SARS-CoV-2, Saliva, nasal swab, gargle lavage, RNA stability, throat swab, 【초록키워드】 Saliva, Healthcare workers, nasal, RT-PCR, healthcare worker, RNA, reverse transcription polymerase chain reaction, polymerase chain reaction, rRT-PCR, stability, Viral load, cycle threshold, reverse transcription, SARS-CoV-2 RNA, agreement, nasal swab, N gene, real-time RT-PCR, gargle, Other, patients, RNA stability, Analysis, Ct values, Chain Reaction, transport medium, specimen collection, normal saline, Transport, workload, Clinical use, no significant differences, no significant difference, significant differences, medium, ORF gene, E gene, specimen, saliva samples, unavailability, sample collection, throat swab, positive COVID-19, polymerase chain, lavage, collected, Sample, conducted, ORF, reduce, subset, processed, diagnosis of COVID-19, NTS, the SARS-CoV-2, 【제목키워드】 nasal, gargle, diagnosis of COVID-19,