The capacity for Alzheimer's disease confirmatory testing in the United States: The current situation and simulations for future increase

Background With recent advances in disease-modifying therapies for Alzheimer's disease (AD), demand for confirmatory biomarker testing such as via cerebrospinal fluid (CSF) analysis or amyloid positron emission tomography (PET) will increase considerably for diagnosis. Objective To assess the current capacity and estimating the anticipated future need of AD confirmatory testing in the United States (US). Methods A population-based decision tree model was employed to simulate the AD diagnostic pathway for patients presenting with symptoms of mild cognitive impairment or mild dementia in primary and secondary care in the US. All patients were assumed to be enrolled in Medicare. The study was conducted from the US payer's perspective over a 5-year period. Four scenarios assessed the impact of different utilization patterns: (1) reference scenario (current use in AD diagnostic pathway: < 1% amyloid-PET; 3.5% CSF analysis); (2) increased CSF analysis utilization scenario (50% utilization); (3) amyloid-PET only; and (4) CSF analysis only. Results Scenario 1 fails to meet the growing demand for AD confirmatory testing (assumed annual care-seeking rate of 50%), with approximately 0.3% of all amyloid-β-positive patients receiving a timely and accurate diagnosis with amyloid-PET, and 1.7% with CSF analysis. Scenarios 2 and 4 resulted in the highest proportion of accurate and timely diagnoses for amyloid-β-positive patients (24.8% and 44.6%, respectively) versus 15.1% of patients in scenario 3. Conclusions It is imperative to address capacity issues for AD confirmatory testing to facilitate timely diagnosis and initiation of amyloid-targeting therapies. Increasing CSF analysis utilization has the capacity to meet this growing demand.