Blood and saliva SARS-CoV-2 antibody levels in self-collected dried spot samples

Abstract

We examined the usefulness of dried spot blood and saliva samples in SARS-CoV-2 antibody analyses. We analyzed 1231 self-collected dried spot blood and saliva samples from healthcare workers. Participants filled in a questionnaire on their COVID-19 exposures, infections, and vaccinations. Anti-SARS-CoV-2 IgG, IgA, and IgM levels were determined from both samples using the GSP/DELFIA method. The level of exposure was the strongest determinant of all blood antibody classes and saliva IgG, increasing as follows: (1) no exposure (healthy, non-vaccinated), (2) exposed, (3) former COVID-19 infection, (4) one vaccination, (5) two vaccinations, and (6) vaccination and former infection. While the blood IgG assay had a 99.5% sensitivity and 75.3% specificity to distinguish participants with two vaccinations from all other types of exposure, the corresponding percentages for saliva IgG were 85.3% and 65.7%. Both blood and saliva IgG-seropositivity proportions followed similar trends to the exposures reported in the questionnaires. Self-collected dry blood and saliva spot samples combined with the GSP/DELFIA technique comprise a valuable tool to investigate an individual’s immune response to SARS-CoV-2 exposure or vaccination. Saliva IgG has high potential to monitor vaccination response wane, since the sample is non-invasive and easy to collect.

Methodological approaches to optimize multiplex oral fluid SARS-CoV-2 IgG assay performance and correlation with serologic and neutralizing antibody responses

“…[28][29][30] To overcome the challenge associated with low total IgG concentrations in saliva compared to blood some have resorted to concentrating saliva, either with or without additional accounting for salivary total IgG, which resulted in increased assay sensitivity but reduced specificity. 31 Despite the lower assay performance most groups found that blood SARS-CoV-2 IgG levels correlate well with salivary IgG levels 32 , however, such findings are often based on very small sample sizes. 31,33,34 Studies with larger sample sizes typically report less robust correlations between saliva and blood antibody levels.…”

Aerosol concentrations and size distributions during clinical dental procedures

“…At the beginning of the COVID-19 pandemic the use of air turbine handpiece and ultrasonic scaler were prohibited in most countries as dental professionals were thought to be more prone to SARS-CoV-2 infection compared to other healthcare occupational groups [ 8 , 9 , 10 ]. However, contrary findings were published as the pandemic evolved and dental professionals had lower SARS-CoV-2 antibody levels compared to other healthcare professionals [ 11 ] and studies indicating dental procedures do not produce much aerosol particles size smaller than 10 μm if high-volume suction or external high-volume extraction device was properly used [ 2 , 3 , 4 , 5 ]. Additionally, personal protective equipment (PPE) in dentistry was improved when FFP-masks, face shields and hair covers were routinely recommended to use in the beginning of pandemic, and studies have been published indicating low numbers of work-related exposures in dental staff [ 12 , 13 ].…”