Tau PET Tracer Distinguishes Between Alzheimer, Non-Alzheimer Disorders

By Reuters Staff

May 15, 2020

NEW YORK (Reuters Health) - The tau PET tracer R0948 F 18 ((18F)R0948) accurately differentiates Alzheimer disease from non-Alzheimer neurodegenerative disorders, researchers report.

Tau-selective PET tracers allow in vivo visualization of tau pathology in neurodegenerative disorders. Tau deposits differ between Alzheimer disease, which contains mainly paired helical filaments (PHF) with a mixture of 3- to 4-repeat tau isoforms, and non-Alzheimer-disease neurodegenerative disorders.

(18F)R0948 is a novel tau PET tracer that is structurally similar to 18F flortaucipir but has more rapid kinetics and less off-target binding in the basal ganglia.

Dr. Antoine Leuzy of Lund University, in Malmoe, Sweden, and colleagues investigated the performance of (18F)R0948 for discriminating Alzheimer disease (AD) from non-AD in patients with neurodegenerative disorders, in individuals with no cognitive impairment, and in comparison with 18F flortaucipir and established MRI and CSF markers.

Tau positivity by (18F)R0948 was almost exclusively observed in Abeta-positive individuals and carriers of the MAPT R406W mutation, which is considered pathogenic for frontotemporal dementia.

(18F)R0948 distinguished AD dementia from non-AD disorders with 91.9% sensitivity, 90.6% specificity and an overall discriminative accuracy of 97%, the researchers report in JAMA Neurology.

The diagnostic performance of (18F)R0948 when separating AD from different types of non-AD disorders was high except when distinguishing AD from dementia with Lewy bodies.

The discriminative ability of (18F)R0948 was lower for the separation of Abeta-positive mild cognitive impairment (MCI) from the non-AD group, with 37.5% sensitivity, 90.1% specificity, and 73% overall discriminative accuracy.

The highest discriminative accuracy of (18F)R0948 (98%) was significantly higher than that of MRI (91%) and CSF measures (94%).

(18F)R0948 showed lower temporal lobe uptake than 18F flortaucipir in a head-to-head comparison.

"The results suggest that (18F)RO948 has high specificity for AD-type PHF tau pathology outside the medial temporal lobe that is seen only in the context of Abeta positivity and certain MAPT mutations," the authors conclude.

The study had no commercial funding.

Dr. Leuzy and senior author Dr. Oskar Hansson did not respond to a request for comments.

SOURCE: https://bit.ly/2AklCD3 JAMA Neurology, online May 11, 2020.