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Ultrasensitive assay for saliva-based SARS-CoV-2 antigen detection
Annie Ren1,2, Dorsa Sohaei1,2, Antigona Ulndreaj2
1Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
Clinical Chemistry and Laboratory Medicine
|February 16, 2022
Summary
A new ultrasensitive saliva test detects SARS-CoV-2 antigens with PCR-level sensitivity. This rapid antigen test (RAT) offers a reliable, easy alternative for frequent mass COVID-19 screening.
Area of Science:
- Infectious Diseases
- Biotechnology
- Molecular Diagnostics
Background:
- Widespread SARS-CoV-2 testing is crucial for identifying asymptomatic and pre-symptomatic individuals.
- Current saliva-based rapid antigen tests (RATs) lack sufficient analytical sensitivity for reliable mass screening.
- There is a need for highly reliable, easy-to-use, and quick diagnostic tests for frequent SARS-CoV-2 testing.
Purpose of the Study:
- To develop and validate an ultrasensitive, saliva-based SARS-CoV-2 antigen assay.
- To achieve analytical sensitivity comparable to PCR-based tests for early detection of SARS-CoV-2.
- To provide a reliable alternative to nasopharyngeal (NP) swab-based tests for frequent mass testing.
Main Methods:
- Development of a novel electrochemiluminescence (ECL)-based immunoassay for SARS-CoV-2 nucleocapsid (N) antigen detection.
- Measurement of N antigen concentration in saliva samples from two independent cohorts (105 and 689 patients).
- Comparison of the novel assay's performance with saliva-based PCR and a widely used point-of-care rapid test.
Main Results:
- The ultrasensitive saliva assay demonstrated an analytical sensitivity of <0.32 pg/mL, equivalent to four viral RNA copies/µL.
- In both cohorts, the assay achieved 92% sensitivity at 100% specificity, correctly identifying samples with high viral loads (up to 35 CT cycles).
- The novel assay is approximately 700-fold more sensitive than the Abbott Panbio Rapid Test and showed high concordance with PCR methods.
Conclusions:
- The developed ultrasensitive, saliva-based SARS-CoV-2 antigen assay is highly sensitive and specific, showing excellent concordance with PCR testing.
- This novel assay addresses the technological gap for reliable, easy, and quick SARS-CoV-2 diagnostics suitable for frequent mass testing.
- The assay is particularly valuable in situations where frequent swabbing compliance may be challenging, offering a more convenient and safer sampling method.
