So, in this study, we evaluated the association between longitudinal plasma pTau217 and amyloid PET. The logic behind it is that, as many of you know, in recent years, we had several studies evaluating the association between plasma pTau217 and amyloid PET cross-sectionally and showing good concordance and good performance. And earlier this year, we also had FDA clearance for using plasma pTau217, meaning that it can be used in clinical workflow to help clinicians to make decisions for the next step...
So, in this study, we evaluated the association between longitudinal plasma pTau217 and amyloid PET. The logic behind it is that, as many of you know, in recent years, we had several studies evaluating the association between plasma pTau217 and amyloid PET cross-sectionally and showing good concordance and good performance. And earlier this year, we also had FDA clearance for using plasma pTau217, meaning that it can be used in clinical workflow to help clinicians to make decisions for the next step. However, there are many things that we still don’t know, and one of them is how these two biomarkers can change together. So, and most importantly, we also want to understand if plasma pTau217 can provide similar information as amyloid PET in the context of clinical trials, which is very important now, especially with the anti-amyloid therapies and these trials that are available. We included individuals from a subsample from ADNI. The advantage of this subsample is that they had three available amyloid PETs and plasma pTau217 measured at the same time in a time interval of 5.5 years. And another advantage of this subsample was that plasma pTau217 was measured using four different platforms. So it provides us also the opportunity to see if the trajectory of plasma pTau217 depends on the platform that’s used for measuring plasma pTau217. In addition to that, we also used a subsample of individuals from HABS-HD cohort to also have anothe cohort to see if we can replicate the results and we can see similar results in both cohorts. Based on what we observed, we saw that in the ADNI cohort there is a weak/moderate association between changes in plasma pTau217 and amyloid PET, but for HABS-HD cohort we only see this pattern in a non-Hispanic white group. It confirms that these two biomarkers show some level of variance longitudinally. However, this alignment is weak and also it’s cohort-dependent. In addition to that, we also checked the individuals who are in the established level of pathology, meaning that they are PET positive and also plasma pTau217 positive. And what we observed that we didn’t see any association in the changes in plasma pTau217 and amyloid PET. It means that when pathology is established, these two biomarkers are depicting or capturing different biological processes. And I would like to emphasize here that these individuals who are in more advanced or established level of pathology are kind of representative of the placebo arm in clinical trials. What we can understand from the lack of association in this specific group is that we cannot use these two biomarkers interchangeably in a longitudinal setting and in the context of clinical trials because they cannot provide similar information for us.
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