It is interesting that about 30% MCI cases with clear (DSI ≥0.83, 5 of 16 cases) and probable (0.67≤ DSI <0.83, 20 of 71 cases) indications of AD did not convert to AD during the 3-year follow-up, even though they did not significantly differ from AD converters in age, gender, presence of APOE4, years of education, concentrations of CSF markers, Scheltens scores, MMSE, and RAVLT results (Figure 1). This evidence concerns the gene APOE and Alzheimer disease.