(1) All studies were evaluated and filtered by STARD criteria and guidelines for diagnostic testing of evidence-based medicine; (2) AD criteria according NINCDS–ADRDA; (3) MCI criteria according Mayo Clinic (i.e., Petersen), or prospective validation after 1 year follow-up); (4) p-tau epitopes are combined (181, 199, 231); (5) studies with data previously published in other works are not included in the MA. The gene discussed is MAPT; the disease is Alzheimer disease.