Plasma biomarkers of tau for the differentiation between slow and fast tau‐PET accumulators

Abstract

AbstractBackgroundPlasma markers of tau are currently being studied as proxies of cerebral neurofibrillary tangle (NFT) accumulation. Phosphorylated tau (pTau) and N‐terminal tau fragment (NTA) assays are associated with present and future tau‐PET load. Our aim was to investigate whether plasma markers could predict whether someone will be a slow or fast accumulator.MethodWe assessed 143 individuals [72 CU, 54 MCI, 17 AD] from the TRIAD cohort, with two available [18F]MK6240 tau‐PET scans and calculated the relative change (Δ[18F]MK6240) between baseline and follow‐up [mean follow‐up time: 2.1 ± 0.7 years]. We used tertiles to divide individuals as slow, medium and fast accumulators. Additionally, we measured baseline plasma pTau181, pTau217, pTau231 and NTA concentrations. We computed the effect size (Cohen’s d) and area under the curve (AUC) for each plasma marker for Δ[18F]MK6240 between slow and fast accumulators. Δ[18F]MK6240 was calculated in Braak stages I/II, III/IV and V/VI.ResultWe first observed that the highest effect size for Δ[18F]MK6240 in Braak I/II was depicted by pTau231. For Δ[18F]MK6240 in Braak III/IV and Braak V/VI, pTau217 presented the highest effect size (Figure 1). Moreover, AUC values were the highest, and highly similar, in ΔBraak I/II for pTau181, pTau217 and pTau231. For ΔBraak III/IV, pTau181 and pTau217 presented the highest values. Finally, AUC for ΔBraak V/VI, pTau231 and NTA had the highest values, which were also similar (Figure 2).ConclusionPlasma pTau biomarkers (181, 217 and 231) are great predictors of fast accumulation in early to middle Braak regions. For late Braak regions, fast accumulation was best predicted by pTau217 and NTA. Plasma markers are able to determine whether someone will be a fast accumulator in a stage‐specific manner. The currently available tau biofluid measures could be used in the clinical and clinical trial settings, as these are less invasive and cheaper than CSF or PET assessments. Especially in the recruitment phase, pTau217 could be used for screening individuals that are more likely to accumulate tau fast.