The Alzheimer disease (AD) treatment landscape is rapidly evolving. Planning is actively underway to bring newly approved amyloid-lowering monoclonal antibodies for early AD into clinical practice.1-4 Full Food and Drug Administration (FDA) approval of lecanemab on July 6, 2023, and subsequent coverage by the Center for Medicare Services has opened a new era in the diagnosis and treatment of AD that poses significant challenges for providers, payers, and health care systems. Given the large number of patients with early AD potentially eligible for this treatment, a major question is how to estimate the number likely to qualify for treatment.5