Usage and positivity rates of Alzheimer's disease biomarkers in a memory clinic.

INTRODUCTION: Usage of biomarker tests for Alzheimer's disease pathology and rates of positivity were assessed at the Washington University Memory Diagnostic Center. METHODS: Patients who underwent at least one biomarker test for clinical purposes between June 2021 and March 2025 were included (n = 1136). Data were retrospectively extracted from electronic health records. RESULTS: The median age was 73.2 years (52% female; 93% White). In total, 455 amyloid positron emission tomography (PET) scans, 505 cerebrospinal fluid tests, and 242 blood tests were performed. The number of biomarker tests increased seven-fold over the past 4 years. The rate of positivity was ≈70% across modalities. Higher rates of biomarker positivity were associated with older age, female sex, and White race; lower rates were associated with hypertension and diabetes. DISCUSSION: Biomarker testing greatly increased following the approval of amyloid-targeting treatments. The overall rate of biomarker positivity was high and varied by demographic factors and medical comorbidities.