Plasma p-tau217 assays effectively predict amyloid status but lack precision for tau staging in Alzheimer's disease.
Level 3 - non-randomized controlled study
Cross-sectional diagnostic accuracy study with an established reference standard (PET) and an independent replication cohort.
PubMed 41784652 · doi:10.1007/s00415-026-13726-z
What was done
Evaluated commercial plasma biomarker assays, primarily p-tau217, against amyloid and tau PET imaging in 229 participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI). The study assessed biomarker accuracy in detecting amyloid status (A+ vs A−T−) and PET-defined tau stages (A+T+ vs A+T−), replicating the results in an independent cohort (n = 334).
What was found
Plasma p-tau217 showed the strongest linear and non-linear associations with amyloid and tau PET. In discriminating A+ from A−T− individuals, p-tau217 achieved an AUC range of 0.85–0.91, higher than other biomarkers (AUC 0.66–0.81). However, accuracy significantly declined when separating A+T+ from A+T− individuals (p-tau217 AUC: 0.69–0.77; other biomarkers: 0.53–0.67; P < 0.05). Findings were confirmed in the independent replication cohort.
Why it matters
While blood p-tau217 tests work well for identifying amyloid pathology, they lack the diagnostic precision to replace tau PET for staging tau pathology severity.
Limits
The abstract does not state confidence intervals, demographic or clinical characteristics (such as baseline cognitive impairment), specific commercial assay brands, or the cutoff criteria used for PET staging.
Cited by
- contradicts Blood-based p-tau217 testing performs as accurately as cerebrospinal fluid analysis and PET tau neuroimaging for Alzheimer's biomarker detection.