Prospective Study Comparing Deep Throat Saliva With Other Respiratory Tract Specimens in the Diagnosis of Novel Coronavirus Disease 2019

Abstract

Background Self-collected specimens has been advocated to avoid infectious exposure to healthcare workers. Self-induced sputum in those with a productive cough, and saliva in those without a productive cough have been proposed, but sensitivity remains uncertain. Methods We performed a prospective study in two regional hospitals in Hong Kong Results We prospectively examined 563 serial samples collected during the virus shedding periods of 50 patients: 150 deep-throat saliva (DTS), 309 pooled-nasopharyngeal (NP) and throat swabs, and 104 sputum. DTS had the lowest overall RT-PCR positive rate (68.7% vs. 89.4% [sputum] and 80.9% [pooled NP and throat swabs]), and the lowest viral RNA concentration (mean log copy/mL 3.54 vs. 5.03 [sputum] and 4.63 [pooled NP and throat swabs]). Analyses with respect to time from symptom onset and severity also revealed similar results. Virus yield of DTS correlated with that of sputum (Pearson correlation index [95% CI]: 0.76 [0.62 – 0.86]). We estimated the overall false-negative rate of DTS could be 31.3%, and increased 2.7 times among patients without sputum. Conclusion DTS produced the lowest viral RNA concentration and RT-PCR positive rate compared to conventional respiratory specimens in all phases of illness. Self-collect sputum should be the choice for patients with sputum.

Evaluation of sample collection and transport strategies to enhance yield, accessibility, and biosafety of COVID-19 RT-PCR testing

“…We found that saliva is an excellent test matrix for the Xpert Xpress SARS-CoV-2 test, providing a sensitivity that is comparable to NP swabs and better than nasal and oral swabs. This finding is consistent with previously published studies using other RT-qPCR modalities [18][19][20][21][22][23] . Although a handful of previous studies have looked at saliva tested in the Xpert SARS-CoV-2 11,24,25 , to our knowledge this study is the first study to comprehensively test multiple non-invasive sampling methods, in the setting of both symptomatic and asymptomatic SARS-COV-2 infection, with and without the use of a sterilizing sample/transport buffer.…”

Diagnosis of SARS-Cov-2 Infection by RT-PCR Using Specimens Other Than Naso- and Oropharyngeal Swabs: A Systematic Review and Meta-Analysis

“…Overall, twenty-one studies had low risk of bias (63.6%) [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 35 , 38 , 39 , 40 , 41 , 42 , 43 ], eleven raised some concerns (33.3%) [ 21 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 36 ] and one had high risk of bias (3.0%) [ 37 ] ( Figure 2 ) (fully detailed in Supplementary S3 , pp. 12).…”

“…Therefore, as a diagnostic specimen, "saliva" deserves a particular attention, and several considerations need to be taken into account. Firstly, most studies accounted for salivary samples circumscribed to the oral region (anterior to the throat) [ 12 , 13 , 15 , 20 , 22 , 26 , 30 , 33 , 34 , 35 , 37 , 38 , 39 , 40 , 42 ], while the remaining studies analyzed DTS/POS with or without pre-throat saliva [ 25 , 27 , 29 , 32 , 41 , 43 ]. This fact is very important as the salivary characteristics and the collection method differ, and the DTS/POS may contain samples other than the oropharyngeal region (naso-pharyngeal or laryngeal-pharyngeal) [ 55 ].…”

“…Aiming at simplifying the sample collection procedure, so that the average person could perform self-sampling, alternative specimens have been tested for the detection of SARS-CoV-2, namely sputum, saliva, tears/conjunctival swab (CS), feces, rectal swab, urine, breast milk, and semen [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. To the best of our knowledge, until now, just one protocol for saliva testing, the SalivaDirect, has been approved by a public health authority, the United States Food and Drug Administration (FDA) [ 44 ].…”

SalivaAll: Clinical validation of a sensitive test for saliva collected in healthcare and community settings with pooling utility for SARS-CoV-2 mass surveillance

“…In a healthcare setting, studies have demonstrated comparable [6][7][8][9] and even higher sensitivity of saliva [10]/ early morning saliva collection [11] compared to NPS samples, as well as reported higher viral titer values in saliva [9]. Conversely, deep-throat saliva [12] and typical saliva samples have also been demonstrated to be less sensitive compared to NPS samples in both healthcare [13] and community settings [14]. Furthermore, saliva samples are difficult to pipet by the testing personnel, which leads to increased processing time [15].…”