Ultrasensitive assay for saliva-based SARS-CoV-2 antigen detection

doi:10.1515/cclm-2021-1142

. 2022 Feb 16;60(5):771-777.

doi: 10.1515/cclm-2021-1142. Print 2022 Apr 26.

Ultrasensitive assay for saliva-based SARS-CoV-2 antigen detection

Annie Ren^{1

2}, Dorsa Sohaei^{1

2}, Antigona Ulndreaj², Oscar D Pons-Belda², Amaia Fernandez-Uriarte², Ioannis Zacharioudakis³, George B Sigal⁴, Martin Stengelin⁴, Anu Mathew⁴, Christopher Campbell⁴, Nikhil Padmanabhan⁴, Daniel Romero⁴, Jessica Joe⁴, Antoninus Soosaipillai⁵, Vathany Kulasingam^{1

6}, Tony Mazzulli^{1

7}, Xinliu A Li⁷, Allison McGeer^{1

7}, Eleftherios P Diamandis^{1

2

6}, Ioannis Prassas^{2

5}

Affiliations

¹ Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
² Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.
³ Biology Department, University of Crete, Heraklion, Crete, Greece.
⁴ Meso Scale Diagnostics, LLC. (MSD), Rockville, MD, USA.
⁵ Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Canada.
⁶ Department of Clinical Biochemistry, University Health Network, Toronto, ON, Canada.
⁷ Department of Microbiology, University Health Network, Mount Sinai Hospital, Toronto, Canada.

PMID: 35170269
DOI: 10.1515/cclm-2021-1142

Free article

Ultrasensitive assay for saliva-based SARS-CoV-2 antigen detection

Annie Ren et al. Clin Chem Lab Med. 2022.

Free article

. 2022 Feb 16;60(5):771-777.

doi: 10.1515/cclm-2021-1142. Print 2022 Apr 26.

Authors

Affiliations

¹ Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
² Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.
³ Biology Department, University of Crete, Heraklion, Crete, Greece.
⁴ Meso Scale Diagnostics, LLC. (MSD), Rockville, MD, USA.
⁵ Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Canada.
⁶ Department of Clinical Biochemistry, University Health Network, Toronto, ON, Canada.
⁷ Department of Microbiology, University Health Network, Mount Sinai Hospital, Toronto, Canada.

PMID: 35170269
DOI: 10.1515/cclm-2021-1142

Abstract

Objectives: Widespread SARS-CoV-2 testing is invaluable for identifying asymptomatic/pre-symptomatic individuals. There remains a technological gap for highly reliable, easy, and quick SARS-CoV-2 diagnostic tests suitable for frequent mass testing. Compared to nasopharyngeal (NP) swab-based tests, saliva-based methods are attractive due to easier and safer sampling. Current saliva-based SARS-CoV-2 rapid antigen tests (RATs) are hindered by limited analytical sensitivity. Here, we report one of the first ultrasensitive, saliva-based SARS-CoV-2 antigen assays with an analytical sensitivity of <0.32 pg/mL, corresponding to four viral RNA copies/µL, which is comparable to that of PCR-based tests.

Methods: Using the novel electrochemiluminescence (ECL)-based immunoassay, we measured the SARS-CoV-2 nucleocapsid (N) antigen concentration in 105 salivas, obtained from non-COVID-19 and COVID-19 patients. We then verified the results with a second, independent cohort of 689 patients (3.8% SARS-CoV-2 positivity rate). We also compared our method with a widely used point-of-care rapid test.

Results: In the first cohort, at 100% specificity, the sensitivity was 92%. Our assay correctly identified samples with viral loads up to 35 CT cycles by saliva-based PCR. Paired NP swab-based PCR results were obtained for 86 cases. Our assay showed high concordance with saliva-based and NP swab-based PCR in samples with negative (<0.32 pg/mL) and strongly positive (>2 pg/mL) N antigen concentrations. In the second cohort, at 100% specificity, sensitivity was also 92%. Our assay is about 700-fold more sensitive than the Abbott Panbio Rapid Test.

Conclusions: We demonstrated the ultrasensitivity and specificity assay and its concordance with PCR. This novel assay is especially valuable when compliance to frequent swabbing may be problematic.

Keywords: SARS-CoV-2; electrochemiluminescence (ECL) immunoassay; mass testing; nasopharyngeal (NP) swab; saliva; sensitivity.

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Comment in

Diagnostic accuracy of the ultrasensitive S-PLEX SARS-CoV-2 N electrochemiluminescence immunoassay.
Lippi G, Henry BM, Montagnana M, Plebani M. Lippi G, et al. Clin Chem Lab Med. 2022 Mar 14;60(6):e121-e124. doi: 10.1515/cclm-2022-0155. Print 2022 May 25. Clin Chem Lab Med. 2022. PMID: 35285218 No abstract available.

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References

1. Medicine, TLR. Realising the potential of SARS-CoV-2 vaccines—a long shot? Lancet Respir Med 2021;9:117. https://doi.org/10.1016/s2213-2600(21)00045-x . - DOI
1. Contreras, S, Dehning, J, Loidolt, M, Zierenberg, J, Spitzner, FP, Urrea-Quintero, JH, et al.. The challenges of containing SARS-CoV-2 via test-trace-and-isolate. Nat Commun 2021;12:378. https://doi.org/10.1038/s41467-020-20699-8 . - DOI - PubMed - PMC
1. Raffle, AE, Pollock, AM, Harding-Edgar, L. Covid-19 mass testing programmes. BMJ 2020;370:m3262. https://doi.org/10.1136/bmj.m3262 . - DOI - PubMed
1. Wyllie, AL, Fournier, J, Casanovas-Massana, A, Campbell, M, Tokuyama, M, Vijayakumar, P, et al.. Saliva or nasopharyngeal swab specimens for detection of SARS-CoV-2. N Engl J Med 2020;383:1283–6. https://doi.org/10.1056/nejmc2016359 . - DOI - PubMed - PMC
1. Medeiros, RC, Nogueira, LC, de Araújo, DN, Costa, K, Pirih, FQ, Luz de Aquino, AR. Saliva as a possible tool for the SARS-CoV-2 detection: a review. Trav Med Infect Dis 2020;38:101920. https://doi.org/10.1016/j.tmaid.2020.101920 . - DOI - PubMed - PMC

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[1] Medicine, TLR. Realising the potential of SARS-CoV-2 vaccines—a long shot? Lancet Respir Med 2021;9:117. https://doi.org/10.1016/s2213-2600(21)00045-x . - DOI

[2] Medicine, TLR. Realising the potential of SARS-CoV-2 vaccines—a long shot? Lancet Respir Med 2021;9:117. https://doi.org/10.1016/s2213-2600(21)00045-x . - DOI

[3] Contreras, S, Dehning, J, Loidolt, M, Zierenberg, J, Spitzner, FP, Urrea-Quintero, JH, et al.. The challenges of containing SARS-CoV-2 via test-trace-and-isolate. Nat Commun 2021;12:378. https://doi.org/10.1038/s41467-020-20699-8 . - DOI - PubMed - PMC

[4] Contreras, S, Dehning, J, Loidolt, M, Zierenberg, J, Spitzner, FP, Urrea-Quintero, JH, et al.. The challenges of containing SARS-CoV-2 via test-trace-and-isolate. Nat Commun 2021;12:378. https://doi.org/10.1038/s41467-020-20699-8 . - DOI - PubMed - PMC

[5] Raffle, AE, Pollock, AM, Harding-Edgar, L. Covid-19 mass testing programmes. BMJ 2020;370:m3262. https://doi.org/10.1136/bmj.m3262 . - DOI - PubMed

[6] Raffle, AE, Pollock, AM, Harding-Edgar, L. Covid-19 mass testing programmes. BMJ 2020;370:m3262. https://doi.org/10.1136/bmj.m3262 . - DOI - PubMed

[7] Wyllie, AL, Fournier, J, Casanovas-Massana, A, Campbell, M, Tokuyama, M, Vijayakumar, P, et al.. Saliva or nasopharyngeal swab specimens for detection of SARS-CoV-2. N Engl J Med 2020;383:1283–6. https://doi.org/10.1056/nejmc2016359 . - DOI - PubMed - PMC

[8] Wyllie, AL, Fournier, J, Casanovas-Massana, A, Campbell, M, Tokuyama, M, Vijayakumar, P, et al.. Saliva or nasopharyngeal swab specimens for detection of SARS-CoV-2. N Engl J Med 2020;383:1283–6. https://doi.org/10.1056/nejmc2016359 . - DOI - PubMed - PMC

[9] Medeiros, RC, Nogueira, LC, de Araújo, DN, Costa, K, Pirih, FQ, Luz de Aquino, AR. Saliva as a possible tool for the SARS-CoV-2 detection: a review. Trav Med Infect Dis 2020;38:101920. https://doi.org/10.1016/j.tmaid.2020.101920 . - DOI - PubMed - PMC

[10] Medeiros, RC, Nogueira, LC, de Araújo, DN, Costa, K, Pirih, FQ, Luz de Aquino, AR. Saliva as a possible tool for the SARS-CoV-2 detection: a review. Trav Med Infect Dis 2020;38:101920. https://doi.org/10.1016/j.tmaid.2020.101920 . - DOI - PubMed - PMC

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Ultrasensitive assay for saliva-based SARS-CoV-2 antigen detection

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