Plasma p217+tau versus NAV4694 amyloid and MK6240 tau PET across the Alzheimer's continuum

We evaluated a new Simoa plasma assay for phosphorylated tau (P-tau) at aa217 enhanced by additional p-tau sites (p217+tau).

Plasma p217+tau levels were compared to ¹⁸F-NAV4694 amyloid beta (Aβ) positron emission tomography (PET) and ¹⁸F-MK6240 tau PET in 174 cognitively impaired (CI) and 223 cognitively unimpaired (CU) participants.

Compared to Aβ- CU, the plasma levels of p217+tau increased 2-fold in Aβ+ CU and 3.5-fold in Aβ+ CI. In Aβ- the p217+tau levels did not differ significantly between CU and CI. P217+tau correlated with Aβ centiloids P = .67 (CI, P = .64; CU, P = .45) and tau SUVR_MT P = .63 (CI, P = .69; CU, P = .34). Area under curve (AUC) for Alzheimer's disease (AD) dementia versus Aβ- CU was 0.94, for AD dementia versus other dementia was 0.93, for Aβ+ versus Aβ- PET was 0.89, and for tau+ versus tau- PET was 0.89.

Plasma p217+tau levels elevate early in the AD continuum and correlate well with Aβ and tau PET.