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. 2020 Oct:131:104593.
doi: 10.1016/j.jcv.2020.104593. Epub 2020 Aug 16.

Evaluation on testing of deep throat saliva and lower respiratory tract specimens with Xpert Xpress SARS-CoV-2 assay

River Chun-Wai Wong  1 , Ann Han Wong  2 , Yolanda Iok-Ieng Ho  2 , Eddie Chi-Man Leung  2 , Raymond Wai-Man Lai  2
Affiliations

Evaluation on testing of deep throat saliva and lower respiratory tract specimens with Xpert Xpress SARS-CoV-2 assay

River Chun-Wai Wong et al. J Clin Virol. 2020 Oct.

Abstract

Background: Xpert® Xpress SARS-CoV-2 assay is only validated on nasopharyngeal specimens for detection of SARS-CoV-2. Other specimen types such as deep throat saliva (DTS), also known as posterior oropharyngeal saliva and lower-respiratorytract specimens (LRT) including sputum, tracheal aspirate and bronchoalveolar lavage are not validated. These non-validated specimen types, however, do have significant diagnostic value.

Objective: Evaluate the performance of Xpert Xpress SARS-CoV-2 assay for detection of SARS-CoV-2 from DTS and LRT specimens.

Methods: 162 specimens from 158 patients with suspected COVID-19 disease were tested with Xpert Xpress SARS-CoV-2 assay. These included 120 DTS and 42 LRT specimens i.e. 35 sputum, 6 tracheal aspirate and one bronchoalveolar lavage. Results were compared to those by the TIB-Molbiol LightMix® SarbecoV E-gene assay.

Results: Xpert Xpress SARS-CoV-2 assay has satisfactory performance when compared with reference method. The positive percent agreement (PPA) of DTS and LRT specimens were 98.86 % & 100 % respectively while the negative percent agreement (NPA) was 100 % for both DTS and LRT specimens.

Conclusions: This study demonstrated with appropriate sample pre-treatment, Xpert Xpress SARS-CoV-2 assay can be used to test on non-validated specimen types including DTS & LRT specimens.

Keywords: Deep throat saliva; Lower respiratory tract specimens; Non-validated specimen types; SARS-CoV-2; Xpert Xpress SARS-CoV-2 assay.

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Conflict of interest statement

The authors report no declarations of interest.

References

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