Data from: 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 highly reproducible over time points, with values
ranging from 0.880 at 36 months to 0.913 at 54 months. Assessing the
healthy control (HC) group only, the same relationships were found.
Conclusions: The current study demonstrates reproducibility of the plasma
assay to discriminate between amyloid-PET positive and negative over three
time points, which can help to substantially reducing the screening rate
of failure (SRF) for clinical trials targeting pre-clinical or prodromal
disease. Classification of evidence: This study provides Class II evidence
that plasma total AB42/AB40 ratio is associated with neocortical amyloid
burden as measured by PET SUVR.