Total Aβ42/Aβ40 ratio in plasma predict amyloid-PET status, independent of clinical AD diagnosis

Background: Research has focussed upon the identification of a blood-based biomarker to inform clinicians on the likelihood of Alzheimer’s disease pathology prior to ordering the CSF and PET testing.
Objective: To explore if the plasma total Aβ42/Aβ40 ratio is a reliable predictor of the amyloid-PET status we have explored the association between these two variables in a subset of the Australian Imaging, Biomarkers and Lifestyle (AIBL) study of ageing cohort.
Methodology: Taking plasma samples at three separate time points, we assessed the total Aβ42/Aβ40 ratio in plasma (TP42/40) with regard to neocortical amyloid beta (Aβ) burden via PET SUVR, and investigated both association with Aβ-PET status and correlation (and agreement) with SUVR.
Results: The TP42/40 plasma ratio was associated with PET status at all time points (p<0.013). Correlations with SUVR were similar across each time point, with Spearman’s Rho reaching -0.64 (p<0.0001). Area under the curve (AUC) values were h...