Neurology Learning NetworkPlasma p-tau217/Aβ42 Test Accuracy Reduced in Patients with Traumatic Brain Injury

✅ Clinical Decision Support / Validated Tool

An FDA-approved plasma p-tau217/Aβ42 ratio accurately identified amyloid-PET positivity in older veterans without traumatic brain injury but demonstrated substantially lower performance among those with prior TBI. The findings suggest that TBI history and severity may influence interpretation of Alzheimer disease blood biomarker results.

Clinical Considerations

• The cross-sectional study included 272 Vietnam War veterans without dementia who underwent amyloid-PET imaging and plasma biomarker testing.
• Plasma p-tau217/Aβ42 accuracy was 90% in participants without TBI, declining to 78% and 63% with increasing TBI severity.
• Reduced performance was driven primarily by lower sensitivity, increasing the possibility of false-negative biomarker results.
• Similar reductions in diagnostic accuracy were observed for both plasma p-tau217 and the Aβ42/40 ratio.

Practice Applications

• Interpret negative Alzheimer blood biomarker results cautiously in patients with prior TBI.
• Recognize TBI severity as a potential modifier of biomarker performance.
• Consider additional diagnostic evaluation when clinical suspicion remains despite negative blood testing.
• Monitor future validation studies examining biomarker accuracy across diverse TBI populations.