The first examined NfL concentrations in an unselected population11 which showed that venous DPS results were very strongly correlated with plasma, where another group showed correlations between plasma and venous DPS NfL in ALS.12 Showing that GFAP can be accurately quantified with finger-prick DPS, alongside NfL, has significant implications. This evidence concerns the gene GFAP and amyotrophic lateral sclerosis.