Set to launch this month, a recently approved blood test to detect biomarkers for Alzheimer’s disease could bring diagnosis into everyday clinical practice. In turn, this may support earlier intervention approaches that may help patients, their families and caregivers. The diagnostic, called a Lumipulse G Plasma Ratio test, is the first of its kind to get marketing clearance from the Food and Drug Administration. Until now, diagnosing Alzheimer’s has often relied on costly and invasive tools like a PET scan or lumbar puncture. The blood test could reduce the need for intrusive diagnostics. Recently approved disease-modifying therapeutics that can modestly reduce the rate of cognitive decline may amplify the importance of having a convenient test.
Alzheimer’s disease affects approximately seven million Americans. By 2050, that number is expected to double. The condition robs people’s memory with symptoms that progressively worsen over time. These include disorientation, changes in mood and behavior, confusion about time and place and eventually difficulty speaking, swallowing and walking.
The newly authorized test achieved roughly 92% accuracy in clinical trials in identifying people who had build-up of two proteins—amyloid and tau—associated with Alzheimer’s disease. The ratio of these substances helps determine the presence of amyloid plaques in the brain. The diagnostic is approved for people ages 55 and up who are already showing signs of cognitive decline.
For patients, this could represent an important step in identifying possible causes, but also help navigate next steps, including potential use of treatment options. The FDA approved drugs Leqembi (lecanemab) and Kisunla (donenamab) in 2023 and 2024, respectively, for patients suffering from early-stage Alzheimer’s disease. These therapeutics can slow disease progression, albeit modestly. They work by removing a sticky protein, beta amyloid plaque, from the brain. Tau “tangles” are also thought to contribute to Alzheimer’s. And in a phase 3 trial, Kisunla was shown to be effective at clearing both beta amyloid and tau.
While treatments can lessen the speed at which cognitive and functional decline, persistent safety worries have plagued the medicines, too. These were highlighted, for instance, when the FDA initially denied approval of Kisunla. The agency questioned the drug’s long-term safety, noting a relatively higher rate of treatment discontinuation due to adverse events such as amyloid-related imaging abnormalities that can lead to brain hemorrhage and swelling. Similar potentially dangerous side effects have also occurred in patients taking Leqembi.
The cost of the Lumipulse test hasn’t been publicly disclosed. Nor is there information regarding whether it will be covered by medical insurance. Presumably it will be considerably less costly per unit than, say, a brain scan. The cost of a dose of Amyvid (florbetapir F 18) used in PET scans to detect amyloid plaque accumulation, for example, is around $1,600 per dose. And the total cost, including use of a PET scanner and overhead, can be several thousand more. Medicare is obligated to cover a limited number of imaging tests for certain patients. When deciding upon coverage parameters for the new blood diagnostic, insurers such as Medicare will likely take into account not only the cost per unit but also the fact that a potentially much greater number of people may take the test.
The blood test isn’t without potential issues. To illustrate, a positive test doesn’t prove someone has Alzheimer’s. And so, the risk of false positives exists. Moreover, as with other tests, the results could trigger anxiety and stigma.
Perhaps more importantly, Alzheimer’s is more complex than the mere existence of amyloid plaque in a person’s brain. While this may be a necessary condition of the disease, it is not a sufficient one. Genetics and other issues such as metabolic disease or even a virus may also play roles.
