Background: Blood-based biomarkers have demonstrated great promise for identifying biomarker-confirmed Alzheimer's disease. We aimed to evaluate whether blood-based biomarkers could optimize the referral of memory clinic patients to a tau-PET exam, which is crucial for prognostic evaluation.
Method: The study measured various plasma biomarkers (Aβ42/Aβ40, pTau181, pTau217, pTau231, NfL, and GFAP) and compared them with tau-PET scan results in patients with subjective cognitive decline, mild cognitive impairment, or dementia. Participants were sourced from the Swedish BioFINDER-2 study (548 individuals) and the TRIAD study (179 individuals). Cutoffs for each biomarker were established at 90%, 95%, and 97.5% sensitivity for detecting tau-PET-positivity. We then calculated the percentage of patients below these cutoffs (to potentially avoid unnecessary tau-PET scans) and the tau-PET-positivity rate among those above the cutoffs.
Result: Plasma pTau217 showed the most promising results. At a 95% sensitivity cutoff in both cohorts, using pTau217 could avoid nearly half of the tau-PET scans while maintaining a tau-PET-positivity rate of approximately 70% in those referred. Furthermore, tau-PET was strongly associated with subsequent cognitive decline. In the BioFINDER-2 cohort, tau-PET predicted cognitive decline only in individuals above the plasma pTau217 referral cutoff, suggesting a more targeted and informative use of tau-PET scans.
Conclusion: Plasma pTau217 demonstrates potential as a guiding biomarker for selecting Alzheimer's disease patients for tau-PET scans, particularly when accurate prognostic information is clinically valuable. This approach could lead to more efficient and informative use of tau-PET scans, avoiding unnecessary procedures in patients unlikely to benefit from them.
© 2024 The Alzheimer's Association. Alzheimer's & Dementia published by Wiley Periodicals LLC on behalf of Alzheimer's Association.