ScienceDaily.com

Using dried blood spot samples (DBS) is an accurate alternative to venous blood in detecting SARS-CoV-2 antibody tests, a new study by immunology experts at the University of Birmingham has found.

Currently, antibody testing for COVID-19 uses serum or plasma, which requires a full intravenous blood sample, collected by a trained phlebotomist. For population-wide or high volume testing, the use of such sampling is limited by logistic challenges, resources, and costs, as well as the risk of SARS-CoV-2 exposure from direct patient contact. In contrast, DBS sampling is simple, inexpensive, and can be self-collected by the patient at home, using a simple finger prick. The sample can then be collected on a forensic grade card before being posted back to labs for processing. This offers exciting possibilities to widen access to antibody testing particularly in more resource-limited countries.

Researchers analyzed serum and DBS samples from volunteers at University Hospitals Birmingham Foundation NHS Trust, some of whom had previously tested positive for SARS-CoV-2 by molecular tests, while the status of other volunteers was either negative or unknown. The anonymized matched serum and DBS samples were then processed using a highly sensitive ELISA test, developed by the University's Clinical Immunology Service in partnership with The Binding Site, which specifically detects antibodies (IgG, IgA, and IgM) to the SARS-CoV-2 trimeric spike protein.

Results showed a significant correlation between matched DBS and serum samples and minimal differences in results observed by sample type, with negligible discordance. Relative to serum samples, DBS samples achieved 98% sensitivity and 100% specificity for detecting anti-SARS-CoV-2 S glycoprotein antibodies. 100% of the PCR-positive samples were also antibody-positive in DBS.

Senior author Dr. Matthew O'Shea from the University's Institute of Immunology and Immunotherapy said: "Our results have demonstrated that dry blood spot sampling not only offers a viable alternative for antibodies testing, but one that overcomes the limitations that current methods can present by eliminating the need for skilled phlebotomists.

"DBS offers the opportunity for wider population-level testing and improved surveillance in vulnerable groups such as patients with chronic conditions, the immunocompromised and the elderly by removing the need to come into contact with a healthcare professional during sample collection."

Co-author Professor Adam Cunningham from the Institute of Immunology and Immunotherapy said: "As well as offering the opportunity for improved population-wide antibody testing in the UK, the simplicity and cost-effectiveness of the dry blood spot method could improve the effectiveness of sampling in low and middle-income countries, among groups where venepuncture is culturally unacceptable or in geographically dispersed populations."