COST EFFECTIVENESS OF NOVEL ALZHEIMER'S DEMENTIA DIAGNOSTICS

Purpose: Cerebrospinal fluid biomarker levels improve the sensitivity and specificity of Alzheimer’s disease (AD) diagnosis, but the test is invasive and costly.   Treatment for AD can delay cognitive and functional decline, improve quality of life, and is cost effective.  We aim to estimate the cost effectiveness of clinical assessment plus cerebrospinal fluid biomarker levels compared to clinical assessment alone for the diagnosis of AD.

Method: We constructed a Markov model to estimate the lifetime costs and quality-adjusted life-years (QALYs) of clinical assessment plus cerebrospinal fluid biomarker levels compared to clinical assessment alone for the diagnosis of AD in a cohort of patients with suspected AD.  We considered the influence of the prevalence of AD in the referred population, the cost of the biomarker test, the quality-of-life reduction associated with the invasiveness of lumbar puncture, and the combination assessment sensitivity and specificity.  Lifetime discounted costs, including those of unpaid caregivers, and health benefits in QALYs were estimated using a U.S. societal perspective.

Result: At an AD prevalence of 15% in the referred population, clinical assessment plus biomarker (sensitivity of 68% and specificity of 93%) costs $1,747 per person less and reduces QALYs by 0.011 when compared to clinical assessment alone (sensitivity of 43% and specificity of 81%).  The cost savings are largely due to the reduction in the number of false positives who receive costly treatment with no utility benefit.  The decrease in QALYs is primarily due to the invasiveness of lumbar puncture (quality-of-life reduction of 0.02 QALYs).  At a willingness to pay of $50,000/QALY or $100,000/QALY, clinical assessment plus biomarker is preferred to clinical assessment alone.  If the prevalence of AD in the referral population is greater than 35%, clinical diagnosis plus biomarker decreases costs and increases QALYs compared to clinical diagnosis alone. Clinical assessment alone is preferred if the quality-of-life reduction from lumbar puncture is greater than 0.03 QALY and for referred populations with low AD prevalence (less than 8% of the population). 

Conclusion: The optimal diagnostic strategy depends on the prevalence of AD in the population and the quality-of-life reduction from lumbar puncture, but it is likely that clinical diagnosis plus biomarker is preferred for patients referred for suspected AD.