MAPT and Alzheimer disease: Difficulty regarding sufficient data extraction was also present in this next study, published in 2019, which examined the p-tau/t-tau ratio at various phosphorylation sites (S400/T304/S404, T181, S396, S404) in the saliva of 46 AD patients, 55 patients with mild cognitive impairment (MCI), and 47 control group participants, using Western blot analysis (manufacturer details not shown) [25].