Figure 4
Dried blood spots obtained via fingerstick show comparable serum neutralisation of SARS-CoV-2 spike to paired serum aliquots. Pseudo-virus particles (PVP) expressing SARS-CoV-2 spike were used to measure the neutralisation capacity of human sera and eluted dried blood spots obtained via fingerstick (FDBS) for 11 participant samples. Neutralisation activity was defined as the serum dilution that reduced PVP infectivity by 50%, 70% or 90% (IC50, IC70 or IC90, respectively). As whole blood contains approximately 55% serum this was accounted for when calculating IC values for FDBS eluate. For each FDBS the exact volumes of blood blotted from the participants’ fingers were not measured therefore two volumes were estimated for FDBS volume. The dotted lines across the graph represent the lower limits of detection, with the limit for sera in orange, DSS eluate in blue, ≈ 15 μL FDBS eluate in yellow and ≈ 25 μL FDBS eluate in brown.
