Abstract
<p>INTRODUCTION Factors underlying discordant visual and quantitative amyloid beta-positron emission tomography (A beta-PET) results and their clinical implications are not well understood. METHODS Participants from the 1Florida Alzheimer's Disease Research Center (1FLADRC) underwent A beta-PET, blood draw, brain magnetic resonance imaging (MRI), and neuropsychological testing. We evaluated differences in demographics, apolipoprotein E (APOE) status, biomarkers, and cognition among older adults with concordant and discordant visual-quantitative A beta-PET. Discordance was defined as positive visual read (V) of A beta-PET with below-threshold Centiloid quantification (Q; CL <25; V+/Q-) or negative visual read with CL >= 25 (V-/Q+). RESULTS We studied 386 participants (mean age +/- SD: 70.7 +/- 7.8, 55.2% female, 44.6% Hispanic White). Compared to V+/Q-, V-/Q+ had a higher frequency of APOE epsilon 4 carriers (40%). Black/African American participants were overrepresented in V-/Q+ (40.9%). Both discordant groups had higher plasma phosphorylated tau 217 (p-tau217) and glial fibrillary acidic protein (GFAP) than V-/Q- but lower than V+/Q+. Discordant groups had greater gray matter volume and better cognitive performance than V+/Q+. DISCUSSION Discordant A beta-PET findings likely hold clinical significance and may reflect early stages of neuropathological progression.</p>