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

Med Microbiol Immunol. 2022 Aug;211(4):173-183. doi: 10.1007/s00430-022-00740-x. Epub 2022 Jun 13.

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.

Keywords: Antibody; Blood; COVID-19; Dried spot sample; Exposure; SARS-CoV-2; Saliva; Vaccination.

MeSH terms

  • Antibodies, Viral
  • COVID-19* / diagnosis
  • Humans
  • Immunoglobulin G
  • SARS-CoV-2*
  • Saliva

Substances

  • Antibodies, Viral
  • Immunoglobulin G