key: cord-0044564-85jbwmfv
authors: Iwasaki, Sumio; Fujisawa, Shinichi; Nakakubo, Sho; Kamada, Keisuke; Yamashita, Yu; Fukumoto, Tatsuya; Sato, Kaori; Oguri, Satoshi; Taki, Keisuke; Senjo, Hajime; Sugita, Junichi; Hayasaka, Kasumi; Konno, Satoshi; Nishida, Mutsumi; Teshima, Takanori
title: Comparison of SARS-CoV-2 detection in nasopharyngeal swab and saliva
date: 2020-06-04
journal: J Infect
DOI: 10.1016/j.jinf.2020.05.071
sha: 362243c897af8bdf937ac81daebfb3382cd6d9c6
doc_id: 44564
cord_uid: 85jbwmfv

nan

In this journal, Azzi et al. reported that saliva was a reliable tool to detect SARS-CoV-2(1). We prospectively compared the efficacy of PCR detection of SARS-CoV-2 between paired nasopharyngeal and saliva samples in 76 patients including ten coronavirus disease 2019 (COVID-19) patients. The overall concordance rate of the virus detection between the two samples reached as high as 97.4% (Table 1) ; we confirmed that saliva is a noninvasive and reliable alternative to nasopharyngeal swabs and facilitate widespread PCR testing in the face of shortages of swabs and protective equipment without posing a risk to healthcare workers.

Nasopharyngeal swab and saliva samples were simultaneously collected from patients suspicious of COVID-19 and those with the diagnosis of COVID-19. This study was approved by the Institutional Ethics Board and informed consent was obtained from all patients. To collect nasopharyngeal samples, the swab was passed through the nostril until reaching the posterior nasopharynx and removed while rotating. Saliva were self-collected by the patients and spit into a sterile PP Screw cup 50 (ASIAKIZAI Co., Tokyo, Japan). 200 L Saliva was added to 600 L PBS, mixed vigorously, then centrifuged at 20,000 X g for 5 minutes at 4 o C, and 140 µl of the supernatant was used as a sample. Real-time reverse transcription-quantitative PCR (RT-qPCR) was conducted according to the manual for the Figure 1A) . The CT values were also not significantly different at earlier time points but tended to be higher in saliva later ( Figure 1B) . Figure 1C shows To our knowledge, a few studies compared viral load between nasopharyngeal and saliva samples. The viral loads were 5-times higher in saliva than in nasopharyngeal samples in one study (5) , whereas they were lower in saliva in two studies (6, 8) . In one study, viral loads were equivalent in symptomatic patients, but lower in asymptomatic patients in saliva(9). Our results showed that the viral load was equivalent at earlier time points but lower in saliva than in nasopharyngeal samples at convalescent phase. Timing of sampling, severity of the disease, different methodologies of saliva collection and processing, different skill of swab sampling may be related to inconsistent results.

Although our study has several limitations due to the small number of samples, there have been few prospective studies to date comparing the two samples. Given the large benefits of saliva collection that does not require health worker specialists and protective equipment, our results together with recent studies support the use of saliva as a noninvasive alternative to nasopharyngeal swabs to greatly facilitate widespread PCR testing in the face of shortages of swabs and protective equipment without posing a risk to healthcare workers.

The authors declare that they have no competing interests. 

Saliva is a reliable tool to detect SARS-CoV-2

Functional assessment of cell entry and receptor usage for SARS-CoV-2 and other lineage B betacoronaviruses

Consistent detection of 2019 novel coronavirus in saliva

Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARS-CoV-2: an observational cohort study

Saliva is more sensitive for SARS-CoV-2 detectionin COVID-19 patients than nasopharyngeal swabs. medRxiv

Saliva as a non-invasive specimen for detection of SARS-CoV-2

Sensitivity of nasopharyngeal swabs and saliva for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

Saliva is less sensitive than nasopharyngeal swabs for COVID-19 detection in the community setting