CSF Aβ, but not p-Tau, Predicted Progression from Amnestic MCI to Alzheimer's Disease Dementia.

The purpose of the study was to determine whether Aβ and p-Tau 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 and p-Tau 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 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-Tau alone did not predict progression to ADD (P = 0.101). The relative risk in those with a p-Tau/Aβ ratio higher than 0.135 was 5.7 times greater (P < 0.001). Aβ and p-Tau 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 strongly predicted progression from aMCI to ADD. p-Tau alone, or its relation to Aβ, was inferior than Aβ alone as a predictor of progression to ADD.