The cut-offs for differential diagnosis between CJD and AD are still not set, ranging between >1072 pg/mL [86] and >1583 pg/mL [87]. Because phosphorylated tau (p-tau) shows a less prominent increase in the CSF in CJD as compared to AD, the t-tau/p-tau ratio (cut-off < 0.075) [88] adds to the sensitivity (around 96%) and specificity (98–100%) [88]. The gene discussed is MAPT; the disease is Creutzfeldt Jacob disease.