Abstract
BackgroundAlzheimer's Disease (AD) affects a growing proportion of the population each year. Novel therapies on the horizon may slow the progress of AD symptoms and avoid cases altogether. Initiating treatment for the underlying pathology of AD would ideally be based on biomarker screening tools identifying pre-symptomatic individuals. Early-stage modeling provides estimates of potential outcomes and informs policy development.MethodsA time-to-event (TTE) simulation provided estimates of screening asymptomatic patients in the general population age ≥55 and treatment impact on the number of patients reaching AD. Patients were followed from AD screen until all-cause death. Baseline sensitivity and specificity were 0.87 and 0.78, with treatment on positive screen. Treatment slowed progression by 50%. Events were scheduled using literature-based age-dependent incidences of AD and death.ResultsThe base case results indicated increased AD free years (AD-FYs) through delays in onset and a reduction of 20 AD cases per 1000 screened individuals. Patients completely avoiding AD accounted for 61% of the incremental AD-FYs gained. Total years of treatment per 1000 screened patients was 2,611. The number-needed-to-screen was 51 and the number-needed-to-treat was 12 to avoid one case of AD. One-way sensitivity analysis indicated that duration of screening sensitivity and rescreen interval impact AD-FYs the most. A two-way sensitivity analysis found that for a test with an extended duration of sensitivity (15 years) the number of AD cases avoided was 6,000-7,000 cases for a test with higher sensitivity and specificity (0.90,0.90).ConclusionsThis study yielded valuable parameter range estimates at an early stage in the study of screening for AD. Analysis identified duration of screening sensitivity as a key variable that may be unavailable from clinical trials.
Highlights
Alzheimer's Disease (AD) affects a growing proportion of the population each year
The increasing age of the general population and the incidence of AD in the elderly means that the burden of AD will continue to increase, with a projected prevalence of 8 million by the year 2050 [1,2]
Of primary significance to this model is that the presence of Alzheimer's disease neuropathology identified on screening would precede the onset of clinically significant symptoms that would be diagnosed as dementia of the Alzheimer's type
Summary
Alzheimer's Disease (AD) affects a growing proportion of the population each year. Novel therapies on the horizon may slow the progress of AD symptoms and avoid cases altogether. In parallel to current drug development efforts aimed at slowing the underlying progression of AD, various biomarkers are currently being researched as diagnostic tools. These biomarkers include a variety of imaging techniques as well as assays that evaluate blood and cerebrospinal fluid levels of markers that are believed to be AD-specific [3,4,5,6,7,8]. The sensitivity of this test for conversion to AD is 0.87 and the specificity is 0.78, representing the current state of knowledge in AD screening
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