Biomarkers

Area of Science:

• Neuroimaging
• Neurology
• Gerontology

Background:

• Traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) are common in military Veterans and may impact amyloid PET interpretation.
• Evaluating the agreement between visual read (VR) and Centiloid (CL) quantification is crucial for accurate Alzheimer's disease (AD) diagnosis.

Purpose of the Study:

• To assess the concordance between amyloid PET visual read and Centiloid quantification in US Vietnam War Veterans.
• To determine if comorbidities like TBI and PTSD affect this agreement.

Main Methods:

• Amyloid PET scans ([¹⁸F]Florbetapir) from the ADNI-DOD cohort were analyzed using both visual read by neurologists and MRI-free Centiloid quantification.
• Discordant scans underwent consensus review. Plasma biomarkers (Ab42/40, p-tau217, NfL, GFAP) and regional SUVR values were also analyzed.

Main Results:

• High agreement (91%) was achieved after consensus review (initial: 86%, κ=0.67; final: κ=0.78).
• Agreement was not significantly affected by cognitive status, TBI, PTSD, or APOE4 status.
• Discrepancies were mainly VR-positive/quantitatively-negative cases, showing focal uptake or posterior patterns, and higher plasma GFAP levels.

Conclusions:

• Amyloid PET visual read and Centiloid quantification demonstrate robust agreement in Veterans, even with comorbidities.
• Visual read can identify early or atypical AD patterns not detected by Centiloid quantification alone.