A Multiplex Noninvasive Salivary Antibody Assay for SARS-CoV-2 Infection and Its Application in a Population-Based Survey by Mail
Background. Salivary antibody immunoassays can be used as non-invasive tools in low-cost epidemiological surveillance of infections including COVID-19 caused by the SARS-CoV-2 virus.
Methods. A multiplexed salivary immunoglobulin (Ig) G immunoassay was developed on a Luminex platform using SARS-CoV-2 structural proteins, including the nucleocapsid (N), spike (S), spike subunits S1 and S2, and receptor binding domain (RBD). Saliva and serum samples from COVID-19 cases and pre-outbreak negative controls were used to develop and validate the assay. A nationwide demonstration survey by mail involving self-collection of saliva from adult COVID-19 cases was also conducted. Random forest models were used for protein ranking.
Findings. Saliva survey by mail had 83% valid sample return rate with 192 samples representing individuals from 38 states included in data analysis. Most participants (93%) reported either no symptoms or mild to moderate symptoms not requiring hospitalization. In a full dataset of 227 outbreak and 285 pre-outbreak saliva samples, the assay’s sensitivity and specificity were 87.1% (95% credible interval 82.1%, 91.7%) and 98.5% (95.0%, 100%). The same assay had 95.9% (92.8%, 98.9%) sensitivity and 100% (98.4%, 100%) specificity in outbreak and pre-outbreak serum samples.
Interpretation. Self-collected saliva samples can be used to study population immune responses to SARS-CoV-2. This non-invasive method enables large-scale population surveys by mail. Furthermore, it may be utilized in underserved communities and disproportionally affected subpopulations to identify risk factors for infection and better characterize public health impacts of the COVID-19 and future pandemics.
Funding. US EPA.