After further excluding apolipoprotein E ε4/ε4 homozygotes and anticoagulant users, 79 patients (6% new patients/15% clinical MCI/AD) remained eligible.<h4>Discussion</h4>Findings indicate limited eligibility for AAT in tertiary memory clinics.<h4>Highlights</h4>Initial eligibility for lecanemab was 8% of all patients and 21% of those with clinical mild cognitive impairment (MCI) or Alzheimer's disease (AD) based on approved guidelines in a tertiary memory clinic population. Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.