key: cord-0760439-jdzul6om authors: Lai, Christopher KC; Lui, Grace CY; Chen, Zigui; Cheung, Yuk-Yam; Cheng, Kwok Chu; Leung, Agnes SY; Ng, Rita WY; Cheung, Jo LK; Yeung, Apple CM; Ho, Wendy CS; Chan, Kate C; Hui, David SC; Tsang, Dominic NC; Chan, Paul KS title: Comparison of Self-collected Mouth Gargle with Deep-throat Saliva Samples for the diagnosis of COVID-19: Mouth gargle for diagnosis of COVID-19 date: 2021-07-25 journal: J Infect DOI: 10.1016/j.jinf.2021.07.012 sha: e2869f23445533ed940cf7ff99556f816a6296df doc_id: 760439 cord_uid: jdzul6om nan Financial support: The study was supported by the Health and Medical Research Fund -Commissioned Research on the Novel Coronavirus Disease (COVID-19) (reference no. COVID190107) from the Food and Health Bureau, Hong Kong SAR Government. We read with interest the study by Zhu et al. 1 that proved saliva as an acceptable alternative to nasopharyngeal or oropharyngeal swabs for diagnosis and monitoring of SARS-Coronavirus-2 (SARS-CoV-2) patients. While saliva is a well-accepted self-collected sample, mouth gargle is a potential alternative with characteristics more favourable for laboratory handling. Mouth gargle are non-viscous in nature, which minimizes cross-contamination during resuspension and transfer that poses risk of generating false-positive results. Furthermore, the non-viscous nature also reduces the We recruited 49 patients (30 females) aged 12-81 (median: 61) years, with seven asymptomatic, 20 mild (no pneumonitis), 15 moderate (pneumonitis), and four had severe disease that required oxygen support, and three were critical and required ventilator support. All participants recovered and discharged. Samples were collected between 1 and 19 days (mean 7 ± 4) from symptom onset. A total of 26 sample-pairs that had adequate volume were additionally tested for inter-laboratory and inter-assay consistencies. We found a strong inter-laboratory correlation when using Cobas 6800 and GenXpert with both sample types with correlation coefficients of > 0.8 ( Figure 2C ). Inter-assay performance comparison by E gene detection using Cobas 6800 and GeneXpert performed in Public Health Reference Laboratory and University Laboratory B again showed no significant difference in diagnostic yield using mouth-gargle and DTS ( Figure 2D ). When analyzing the diagnostic yield among various clinical situations, we found that the diagnostic yield of DTS was significantly higher in patients with respiratory symptoms, but there was no significant difference in asymptomatic patients and those who were symptomatic but without respiratory symptoms (Supplementary figure 3) Our study found that the positive rate for SARS-CoV-2 RNA detection from mouth gargle samples was similar to paired deep-throat saliva (DTS) samples collected from patients with active COVID-19 infection irrespective of the laboratory or assay used. Mouth gargle had been shown to be a suitable sample for diagnosis of COVID-19 and respiratory pathogens 6, 7 . Previous studies have shown that gargle samples are comparable, but with slightly higher cycle threshold (Ct) values than those of nasopharyngeal and oropharyngeal swabs 8 . Mouth gargle samples are easy to collect, acceptable to patients 2 , and have the advantage over saliva that it is non-viscous and can dilute inhibitors present in the samples. Our study has the strength of being prospective, inclusion of a wide age range (12 to 81 years), wide spectrum of clinical severity (from asymptomatic to critically ill), and covering all stage of illness (from 1 to 19 days of onset). There are limitations in our study. First, our cohort were all confirmed COVID-19 patients, thus we cannot analyze specificity. Secondly, we did not specify the sequence of mouth gargle and DTS collection; however, we gave explicit instructions to separate the collection of the specimens to be at least 30 minutes apart, which should negate the collection sequence bias. In conclusion, our findings suggested mouth gargle showed excellent correlation with DTS and can be a choice of self-collected specimen for mass screening of asymptomatic individuals. Viral dynamics of SARS-CoV-2 in saliva from infected patients Self-Collected Saline Gargle Samples as an Alternative to Health Care Worker-Collected Nasopharyngeal Swabs for COVID-19 Diagnosis in Outpatients Gargle Lavage as a Safe and Sensitive Alternative to Swab Samples to Diagnose COVID-19: A Case Report in Japan Clinical Characteristics of Imported Cases of Coronavirus Disease 2019 (COVID-19) in Jiangsu Province: A Multicenter Descriptive Study Viral dynamics of SARS-CoV-2 across a spectrum of disease severity in COVID-19 Gargle Lavage as a Safe and Sensitive Alternative to Swab Samples to Diagnose COVID-19: A Case Report in Japan Comparison of gargle samples and throat swab samples for the detection of respiratory pathogens Gargle lavage as a viable alternative to swab for detection of SARS-CoV-2 Reference Laboratory (Cobas 6800) positive rate for mouth gargle: 96.3% (95% CI 90.0 -98.6), and DTS: 95.4% (95% CI 89.7-98.0). Reference Laboratory (GeneXpert) positive rate for mouth gargle: 94.5% (95% CI: 88.5-97.5), and DTS: 96.3% (95% CI: 90.9 -98.6). Reference Laboratory (In-house method) positive rate for mouth gargle: 95.4% (95% CI DTS -Deep-throat saliva samples Gargle -mouth gargle samples. Fisher test was used to assess the difference in positive rates between detection assays and/or specimens. The 95% confidence interval (CI) was calculated using epi Figure 2 -Comparison of diagnostic yield between sample types, assays, and laboratories A Comparison of diagnostic yield of the 109 mouth gargle and DTS sample pairs by test method DTS, Deep-throat saliva **** P ≤ 0.0001. Comparisons of viral concentration between detection assays and/or specimens were performed using non-parametric Wilcoxon rank-sum test (unpaired) or Wilcoxon signed rank test (paired) Correlation analysis between 109 mouth gargle and DTS sample pairs by test method. Correlation performed by Spearman's correlation index; R2adj, Adjusted R-squared. Spearman's rho and linear regression were used to evaluate their associations. A two-sided p value of < 0.05 was considered statistically significant C -Inter-laboratory comparison of Cobas 6800 and GeneXpert of 26 paired samples by Reference Laboratory and University Laboratory B. Correlation performed by Spearman's correlation index Adjusted R-squared. DTS -deep-throat saliva Gargle -mouth gargle. Spearman's rho and linear regression were used to evaluate their associations. A two-sided p value of < 0.05 was considered statistically significant Midline: median; Box: interquartile range; DTSdeep-throat saliva; Gargle -mouth gargle. Comparisons of viral concentration between detection assays and/or specimens were performed using non-parametric Wilcoxon rank-sum test (unpaired) or Wilcoxon signed rank test (paired) None declared