CSF Aβ_1–42, but not p-Tau₁₈₁, Predicted Progression from Amnestic MCI to Alzheimer’s Disease Dementia

The purpose of the study was to determine whether Aβ_1–42 and p-Tau₁₈₁ cerebral spinal fluid (CSF) levels can predict progression from amnestic mild cognitive impairment (aMCI) to Alzheimer’s disease dementia (ADD) in a 3-year follow-up study. All participants were evaluated blindly by a behavioral neurologist and a neuropsychologist, and classified according to the Petersen criteria for aMCI and according to the Clinical Dementia Rating (CDR) scale. Individuals were also submitted to lumbar puncture at baseline. Levels of Aβ_1–42 and p-Tau₁₈₁ were measured by immunoenzymatic assay. Values were adjusted for age and sex. Thirty-one of 33 (93.9%) participants completed follow-up. Approximately 39% of aMCI individuals progressed to ADD. The relative risk of developing ADD in those with Aβ_1–42 CSF levels lower than 618.5 pg/mL was 17.4 times higher than in those whose levels were higher than 618.5 pg/mL (P = 0.003). p-Tau₁₈₁ alone did not predict progression to ADD (P = 0.101). The relative risk in those with a p-Tau₁₈₁/Aβ_1–42 ratio higher than 0.135 was 5.7 times greater (P < 0.001). Aβ_1–42 and p-Tau₁₈₁ explained 40.1% of the verbal memory test subscore of the Consortium to Establish a Registry for Alzheimer’s Disease (ΔCERADs) variance (P = 0.008). Aβ_1–42 strongly predicted progression from aMCI to ADD. p-Tau₁₈₁ alone, or its relation to Aβ_1–42, was inferior than Aβ_1–42 alone as a predictor of progression to ADD.