The role of mouthwash sampling in SARS-CoV-2 diagnosis

Abstract

Background The current practice of COVID 19 diagnosis worldwide is the use of oro nasopharyngeal (ONP) swabs. Our study aim was to explore mouthwash (MW) as an alternative diagnostic method, in light of the disadvantages of ONP swabs. Methods Covid-19 outpatients molecular confirmed by ONP swab were repeatedly examined with ONP swab and MW with normal saline (0.9%). Other types of fluids were compared to normal saline. The Cq values obtained with each method were compared. Results Among 137 pairs of ONP swabs and MW samples, 84.6% (116/137) of ONP swabs were positive by at least one of the genes (N, E, R). However MW detected 70.8% (97/137) of samples as positive, which means 83.6% (97/116) out of positive ONP swabs, missing mainly Cq value>30. In both methods, the N gene was the most sensitive one. Therefore MW samples targeting N gene, which was positive in 95/137 (69.3%), is comparable to ONP-swabs targeting E and R genes which gave equal results; 95/137 (69.3%) and 90/137 (65.7%) respectively. Comparing saline MW to distilled water gave equal results, while commercial mouth-rinsing solutions were less sensitive. Conclusions MW with normal saline, especially when tested by N gene, can effectively detect COVID 19 patients. Furthermore, this method was not inferior when compared to R and E genes of ONP swabs, which are common targets in many laboratories around the world.

Performance of saline and water gargling for SARS-CoV-2 reverse transcriptase PCR testing: a systematic review and meta-analysis

“…After screening the titles and abstracts of the remaining articles, 45 full texts were screened (figure 1). On the basis of our selection criteria, 27 of those studies were excluded and 18 studies [28,29,35,36,[46][47][48][49][50][51][52][53][54][55][56][57][58][59] met our inclusion criteria (table 1). One study examined two study populations, of suspected infection and of confirmed cases, which were analysed separately [59].…”

“…Of these 19 study populations, seven assessed the diagnostic performance of gargle in populations with suspected infection [28,49,50,54,55,57,59], and 12 assessed the use of gargle for monitoring viral shedding in populations already confirmed to have SARS-CoV-2 infections, either as hospital inpatients or after being discharged (table 1) [29, 35, 36, 46-48, 51-53, 56, 58, 59]. Regarding the study location, there were five studies from Canada [28,47,50,52,57], six from Germany [36,48,49,51,54,56] and with the rest (seven) from Finland [29], Turkey [55], China [46], Korea [58], Indonesia [59], Israel [53] and India [35]. These studies spanned from 23 March 2020 to 19 July 2021, covering the period of different prevailing SARS-CoV-2 variants, from the ancestral strain, alpha variant, to its delta variant.…”

“…Besides two that did not specify participants' age [50,56], all reviewed studies included an adult population, among which eight also included children aged below 18 years [28,36,47,48,52,54,57,59]. 12 studies [28,29,35,46,47,49,51,52,[54][55][56]58] used NPS and six studies [36,48,50,53,57,59] used ONPS, all collected by HCWs, as the reference gold standard. A total of 8888 clinical samples were included in our analysis, including 4444 NPS/ONPS as control, and 4444 gargle samples for testing (1187 saline gargles, 2711 water gargles and 546 gargles without specification).…”

Direct comparison of Altona-SARS-CoV-2 dual target RT-qPCR Assay with commercial LAMP Assay using throat washes in health care staff testing

“…Second, the method was rapidely available and independent of the most limited resource in the early phase of the pandemics besides PCR reagents, namely swabs. Meanwhile several studies have been published that also made use of throat washes or saliva, although these studies suggested to the community that this sampling procedure was entirely novel [14] , [15] , [16] , [17] , [18] .…”

Evaluating Saliva Sampling with Reverse Transcription Loop-mediated Isothermal Amplification to Improve Access to SARS-CoV-2 Diagnosis in Low-Resource Settings

“… 23 Previous studies indicated that sample collection can be feasibly improved to increase the sensitivity of saliva for PCR by using a saliva swab and supervised self-saliva collection, 26 self-collected deep throat saliva, 24 , 25 , 27 or rinse–gargle saliva. 28 , 29 Additional improvements of the LAMP method include the selection of alternative gene targets, such as the N gene or simultaneously use of multiple genes as targets such as E, N, and Orf, 30 – 33 as well as optimized sample processing to minimize interference from the specimen pH, especially for FS, with the colorimetric method. Other enhancements could include the use of a thermal cycle machine, a digital or fluorescence reader for amplification detection, and insulated containers to stabilize the incubation temperature for the LAMP reaction.…”