Self-sampling of capillary blood for serological testing of SARS-CoV-2 by COVID-19 IgG ELISA

Abstract

Serological testing is emerging as a powerful tool to progress our understanding of COVID-19 exposure, transmission and immune response. Large-scale testing is limited by the need for in-person blood collection by staff trained in venepuncture. Capillary blood self-sampling and postage to laboratories for analysis could provide a reliable alternative. Two-hundred and nine matched venous and capillary blood samples were obtained from thirty nine participants and analysed using a COVID-19 IgG ELISA to detect antibodies against SARS-CoV-2. Thirty seven out of thirty eight participants were able to self-collect an adequate sample of capillary blood (≥50 μl). Using plasma from venous blood collected in lithium heparin as the reference standard, matched capillary blood samples, collected in lithium heparin-treated tubes and on filter paper as dried blood spots, achieved a Cohen′s kappa coefficient of >0.88 (near-perfect agreement). Storage of capillary blood at room temperature for up to 7 days post sampling did not affect concordance. Our results indicate that capillary blood self-sampling is a reliable and feasible alternative to venepuncture for serological assessment in COVID-19.

Twelve lateral flow immunoassays (LFAs) to detect SARS-CoV-2 antibodies

“…Sera from patients with RT-qPCR confirmed SARS-CoV-2 infection (n=84) were provided by Liverpool Clinical Laboratories (LCL) as leftover diagnostic samples. Participants with RT-qPCR confirmed SARS-CoV-2 infection who did not result in hospital attendance (n=12) were also recruited (7). In addition, the NIBSC COVID-19 convalescent plasma panel, human (20/118), as well as NIBSC 20/130 plasma positive control were used for the evaluation.…”