1.DBS in Direct to Consumer testing
Clearly this is one advantage to filter paper blood spots. Having seen problems in a newborn screening laboratory where the DBS weren't necessarily collected following established protocols (and this was by some experts in nurserys) I worry when consumers perform these tasks. Issues include double spotting, insufficient blood, serum rings, altering the paper by scratching, incomplete dryness.... etc. For very quantitative metabolite assays it could be an issue.
2. Non Cellulose Cards...
Interesting... a reduction of Ion suppression should occur in cellulose paper (current paper). An improvement of extraction efficiency is of most interest although for many of the metabolites in newborn screening, that extraction was quite good (most 90% or better). The issue is volume, standardization and quality control... that has to be established.