Alzheimer’s Disease, the most common cause of dementia, is a progressive disease that mostly affects individuals aged 65 and over. As a progressive disease, it worsens over time, gradually interfering more and more with daily life and making even basic functions impossible. Symptoms that start as difficulty remembering new information, confusion, and mood changes devolve into even worse versions of themselves. People with Alzheimer’s may feel highly disoriented even in their own homes, they may feel unreasonable suspicion and animosity towards their family and caregivers, they may feel more and more confused about everyday events, and even have difficulty speaking as their brain cells lose function and eventually die.
The root causes of Alzheimer’s are not yet fully understood, but the most likely causes and currently accepted indicators are formations in the brain called plaques and tangles. Plaques are deposits of the beta-amyloid protein that build up in between neurons, and tangles are twisted fibers of the tau protein that build up inside cells. The amyloid plaques are exactly what have been used to try to diagnose Alzheimer’s until recently; diagnosis is usually not clear-cut or easy to do, but PET scans of the brain are able to detect and image plaques, which can help in predicting Alzheimer’s disease even before symptoms start to occur. Another way of testing for Alzheimer’s has been done through FDA-authorized tests done with cerebrospinal fluid, obtained through a spinal tap.
Neither of these previous methods of testing for Alzheimer’s are ideal: PET scans are expensive, time-consuming, and expose the patient to radiation (since they require injection of a safe, although radioactive tracer into the patient). Meanwhile, cerebrospinal fluid samples are difficult to obtain, requiring an invasive procedure called a spinal tap, where a thin needle is inserted into the spinal region in a lumbar puncture — not your average 10-minute blood test.
The new test that was approved by the Food and Drug Administration (FDA) in 2025 is easier, done with only a simple blood draw. Called the G pTau217/ß-Amyloid 1-42 Plasma Ratio test, it measures a ratio between the tau and amyloid proteins found in the blood plasma. This ratio has been shown to be correlated to the presence or absence of amyloid plaques in the brain in a clinical study involving 499 individual plasma samples. Importantly, the test is meant to be performed on individuals who are already showing symptoms of cognitive decline and are over the age of 55. It is not for testing young people to predict future Alzheimer’s; unfortunately, science is not able to do that yet. However, it can be very useful for diagnosing the cause of cognitive decline in patients in a quick and accessible way, and it can help doctors or caregivers come up with treatment plans.
The main risks of the test are obtaining false positives or false negatives, which means that there are no potential health drawbacks that would give someone reason to not undergo testing. Dr. Jeff Gelblum, an Alzheimer’s specialist, believes that this new test will make both Alzheimer’s diagnosis and treatment more accessible and widespread. Although there is no cure for Alzheimer’s disease, treatments do exist for mitigating its effects. Different kinds of cognitive therapies or activities may help, and there are also medications that can increase levels of acetylcholine in the brain to help maintain communication between neurons. These medications can only be prescribed to someone diagnosed with Alzheimer’s; that’s why it is important to have easy and accessible testing options that can help diagnose someone. The FDA approval of the new plasma ratio test may be a small step in the bigger fight against Alzheimer’s, but it is an important one.
