ABSTRACT
The importance of easily accessible, noninvasive samples, such as saliva, to effectively monitor serum antibody levels has been underscored by the SARS-CoV-2 (COVID-19) pandemic. Although a correlation between saliva and serum antibody titers has been observed, the ability to predict serum antibody levels from measurements in saliva is not well established. Herein, the authors demonstrate that measurements of SARS-CoV-2 antibody levels in both saliva and nasal specimens can be used to accurately determine serum levels by utilizing endogenous total IgG as an internal calibrator. They postulate that this method can be extended to the measurement of many different antibody analytes, making it of high interest for antibody therapeutic drug monitoring applications.