Sensitive Detection of SARS-CoV-2-Specific Antibodies in Dried Blood Spot Samples

Abstract

Dried blood spot (DBS) samples can be used for the detection of severe acute respiratory syndrome coronavirus 2 spike antibodies. DBS sampling is comparable to matched serum samples with a relative 98.1% sensitivity and 100% specificity. Thus, DBS sampling offers an alternative for population-wide serologic testing in the coronavirus pandemic.

Keywords: COVID-19; DBS; SARS-CoV-2; antibody; coronavirus disease; dried blood spot; respiratory infections; severe acute respiratory syndrome coronavirus 2; viruses; zoonoses.

Figure 1

Elution of SARS-CoV-2 anti-spike glycoprotein antibodies from DBS samples, showing 3-fold DBS eluate (A) (initial 1:3 dilution) and serum (B) (initial 1:15 dilution) titrations. Dashed line indicates pre–August 2019 DBS samples (n = 11). Red circles indicate PCR-positive samples (n = 5). Black circles indicate PCR-unknown samples (n = 11), from matched contemporaneous samples. All samples were selected at random for inclusion. DBS, dried blood spot; OD₄₅₀, optical density at 450 nm; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Figure 2

Effectiveness of DBS sampling for SARS-CoV-2 anti-spike glycoprotein detection. A) Correlation between matched DBS eluate (1:10) and serum (1:100) OD₄₅₀ ELISA results (n = 87). Red circles indicate PCR-positive samples (n = 31). Black circles indicate PCR-unknown samples (n = 56). B) Bland-Altman mean-difference comparison of DBS eluate (1:10) and serum (1:100) OD₄₅₀ ELISA results (dashed lines indicate 95% limits of agreement [−0.281 to 0.504]). DBS, dried blood spot; OD₄₅₀, optical density at 450 nm; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.