INTRODUCTION: Blood-based biomarkers are the next challenge for Alzheimer's disease (AD) diagnosis and prognosis.
METHODS: Mild cognitive impairment (MCI) participants (N = 485) of the BALTAZAR study, a large-scale longitudinal multicenter cohort, were followed-up for 3 years. A total of 165 of them converted to dementia (95% AD). Associations of conversion and plasma amyloid beta (Aβ) , Aβ , Aβ /Aβ ratio were analyzed with logistic and Cox models.
RESULTS: Converters to dementia had lower level of plasma Aβ (37.1 pg/mL [12.5] vs. 39.2 [11.1] , P value = .03) and lower Aβ /Aβ ratio than non-converters (0.148 [0.125] vs. 0.154 [0.076], P value = .02). MCI participants in the highest quartile of Aβ /Aβ ratio (>0.169) had a significant lower risk of conversion (hazard ratio adjusted for age, sex, education, apolipoprotein E ε4, hippocampus atrophy = 0.52 (95% confidence interval [0.31-0.86], P value = .01).
DISCUSSION: In this large cohort of MCI subjects we identified a threshold for plasma Aβ /Aβ ratio that may detect patients with a low risk of conversion to dementia within 3 years.