Fig. 1

DBS elution from Whatman^® 903 protein sample cards. DBS were eluted from sample cards by the method of Klüber (Klüber, J.K., Master’s Thesis, unpublished): a make standardized holes with a punch; b transfer paper disks; c add nuclease free water and incubate for 60 min at 72 °C, vortex every 15 min; d collect the supernatant after centrifugation; e transfer supernatant to new tube and store at − 20 °C