Sensitive Serology Measurements in the Saliva of Individuals with COVID-19 Symptoms Using a Multiplexed Immunoassay.

Background: There are numerous benefits to performing salivary serology measurements for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen for coronavirus disease 2019 (COVID-19). Here, we used a sensitive multiplex serology assay to quantitate salivary IgG against 4 SARS-CoV-2 antigens: nucleocapsid, receptor-binding domain, spike, and N-terminal domain.
Methods: We used single samples from 90 individuals with COVID-19 diagnosis collected at 0 to 42 days postsymptom onset (PSO) and from 15 uninfected control subjects. The infected individuals were segmented in 4 groups (0-7 days, 8-14 days, 15-21 days, and >21 days) based on days PSO, and values were compared to controls.
Results: Compared to controls, infected individuals showed higher levels of antibodies against all antigens starting from 8 days PSO. When applying cut-offs with at least 93.3% specificity at every time interval segment, nucleocapsid protein serology had the best sensitivity at 0 to 7 days PSO (60% sensitivity [35.75% to 80.18%], ROC area under the curve [AUC] = 0.73, P = 0.034). Receptor-binding domain serology had the best sensitivity at 8 to 14 days PSO (83.33% sensitivity [66.44%-92.66%], ROC AUC = 0.90, P < 0.0001), and all assays except for N-terminal domain had 92% sensitivity (75.03%-98.58%) at >14 days PSO.
Conclusions: This study shows that our multiplexed immunoassay can distinguish infected from uninfected individuals and reliably (93.3% specificity) detect seroconversion (in 60% of infected individuals) as early as the first week PSO, using easy-to-collect saliva samples.
Competing Interests: Authors’ Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts of interest: Employment or Leadership: A. Mathew, C. Campbell, M. Stengelin, G. Sigal, J. Joe, D. Romero, and N. Padmanabhan were employees of Meso Scale Diagnostics, LLC. V. Kulasingam, The Journal of Applied Laboratory Medicine, AACC. Consultant or Advisory Role: V. Kulasingam receives consulting fees from Abbott Diagnostics (no fees were received for this project). E.P. Diamandis holds an advisory role with Abbott Diagnostics and a consultant role with Imaware Diagnostics (no fees were received for this project). Stock Ownership: None declared. Honoraria: None declared. Research Funding: This project has been funded in part with federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under Contract No. HHSN272201700013C. A. Ulndreaj is supported by a postdoctoral fellowship from the University of Toronto’s Medicine by Design initiative, which receives funding from the Canada First Research Excellence Fund. Expert Testimony: None declared. Patents: None declared.
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