Considering the spectrum of diseases, it is clear that the assay significantly distinguishes GRN mutation carriers, either symptomatic or pre-symptomatic, from every other disease type (p<0.0001 for GRN and Pre-GRN vs. AD, bvFTD, PPA, CBS, PSP and Controls; p<0.001 vs. C9orf72 mutation carriers; p<0.05 vs. pre-C9orf72). Here, GRN is linked to Alzheimer disease.