Available online 31 December 2022, 113420

Dried blood spots can readily be used to assess COVID-19 antibody status.

Dried blood spots demonstrate high agreement with serum for COVID-19 IgG testing.

Dried blood spots can be stored at room temp for at least 28 days before testing.

Dried blood spot collections require less resources compared to blood draws.

Optimal test cut-off values should independently be determined for DBS collections.

Serologic analysis is an important tool towards assessing the humoral response to COVID-19 infection and vaccination. Numerous serologic tests and platforms are currently available to support this line of testing. Two broad antibody testing categories are point-of-care lateral flow immunoassays and semi-quantitative immunoassays performed in clinical laboratories, which typically require blood collected from a finger-stick and a standard venipuncture blood draw, respectively. This study evaluated the use of dried blood spot (DBS) collections as a sample source for COVID-19 antibody testing using an automated clinical laboratory test system.

Two hundred and ninety-four participants in the BLAST COVID-19 seroprevalence study (NCT04349202) were recruited at the time of a scheduled blood draw to have an additional sample taken via finger stick as a DBS collection. Using the EUROIMMUN assay to assess SARS-CoV-2 anti-spike IgG status, DBS specimens were tested on 7, 14, 21, and 28 days post- collection and compared to the doi:10nce serum sample obtained from a blood draw for the BLAST COVID-19 study.

SARS-CoV-2 anti-spike IgG status from DBS collections demonstrated high concordance with serum across all time points (7–28 days). However, the semi-quantitative value from DBS collections was lower on average than that from serum, resulting in increased uncertainty around the equivocal-to-positive analytical decision point.

DBS collections can be substituted for venipuncture when assaying for COVID-19 IgG antibody, with samples being stable for at least 28 days at room temperature. Finger-stick sampling can therefore be advantageous for testing large populations for SARS-CoV-2 antibodies without the need for phlebotomists or immediate processing of samples. We have high confidence in seropositivity reported from DBS collections, although the reduced semi-quantitative value may cause some low-level positives to fall into the equivocal or even negative range.

Dried blood spot

COVID-19

COVID-19 antibody

SARS-CoV-2 IgG

© 2022 Published by Elsevier B.V.