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Comparative Study
. 2021 Apr 10;13(4):653.
doi: 10.3390/v13040653.

Comparison of Throat Washings, Nasopharyngeal Swabs and Oropharyngeal Swabs for Detection of SARS-CoV-2

Florian Hitzenbichler  1 , Stilla Bauernfeind  1 , Bernd Salzberger  1 , Barbara Schmidt  2   3 , Jürgen J Wenzel  3
Affiliations
Comparative Study

Comparison of Throat Washings, Nasopharyngeal Swabs and Oropharyngeal Swabs for Detection of SARS-CoV-2

Florian Hitzenbichler et al. Viruses. .

Abstract

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) RNA is detected by reverse-transcription quantitative real-time PCR (RT-qPCR) from respiratory specimens. This study compares throat washings (TW), nasopharyngeal swabs (NS) and oropharyngeal swabs (OS). A total of 102 samples from 34 adult patients with confirmed SARS-CoV-2 infection were analysed by RT-qPCR with absolute quantification. The median concentrations and diagnostic sensitivities were 5.8×104 copies/mL, 85% (NS), 1.4×104, 79% (OS) and 4.3×103, 85% (TW). Concentration differences were significant between NS and TW (P = 0.019). Saliva (SA) was available from 21 patients (median 3.4×103). OS and TW can be considered for SARS-CoV-2 diagnostics, although with slightly lower concentrations.

Keywords: COVID-19; PCR; RT-qPCR; SARS-CoV-2; diagnostic sensitivity; nasopharyngeal swab; nucleic acid test; oropharyngeal swab; saliva; throat washing.

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Conflict of interest statement

Hitzenbichler received payments for lectures by MSD Sharp and Dohme and travel grants by Gilead Sciences. Salzberger received payments for lectures by Falk Foundation and consulting fees by Sanofi and GSK. These companies had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
SARS-CoV-2 RNA concentrations in samples of 34 study participants. Measurements are separated into sampling site groups (TW, throat washing; NS, nasopharyngeal swab; OS, oropharyngeal swab). Samples with the result not detected were set to 100 cp/mL and are plotted below the dashed lines. (A) Levels of SARS-CoV-2 viral loads across sampling sites. The respective median concentrations are shown as horizontal lines. The statistically significant difference between the groups was assessed by post-hoc tests based on the linear mixed-effects model and is indicated by a horizontal line with the corresponding P value < 0.05 on top of the data panels. (B) Concentration patterns A–F as found by combinatorial analysis of the quantitative results. Data from six subjects with ≤1 positive result are not shown. (C) comparative SARS-CoV-2 RNA quantification plots, sorted by concentration pattern and decreasing median viral load. Subject identification numbers are indicated on the x-axis.
Figure 2
Figure 2
SARS-CoV-2 RNA concentrations in samples of 21 study participants. Measurements are separated into sampling site groups (TW, throat washing; NS, nasopharyngeal swab; OS, oropharyngeal swab; SA, saliva). Connected datapoints represent results from one patient. Samples with the result not detected were set to 100 cp/mL and are plotted below the dashed lines. (A) Levels of SARS-CoV-2 viral loads across sampling sites. The respective median concentrations are shown as horizontal lines. No statistically significant differences between the four sampling groups were found by linear mixed-effects model analysis. (B) comparative SARS-CoV-2 RNA quantification plots, sorted by concentration pattern and decreasing median viral load. Subject identification numbers are indicated on the x-axis.
See this image and copyright information in PMC

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