5 Things You Need to Know About Blood Tests for Alzheimer’s

The gold-standard methods for diagnosing Alzheimer’s disease are lumbar punctures and PET brain scans. But these methods can be uncomfortable — not to mention expensive and hard to access. Even though amyloid PET scans are now covered by Medicare, patients may still need to travel hours to a hospital or medical center with the medical equipment needed to do the test. Thus, there is a great deal of research being done into easier, more accessible diagnostics, including Alzheimer’s blood tests. 

Blood tests provide a proxy of amyloid levels in the brain. They are quicker to administer than a PET scan, and may allow for more people to be screened for the disease. Several experts have told Being Patient they expect blood tests to be adopted into regular clinical practice for Alzheimer’s diagnosis within the next few years.

At the moment, none of these tests are covered by the Centers for Medicare & Medicaid Services. But that doesn’t mean consumers aren’t able to get one: Currently, there are a number of tests commercially available in the U.S. — some via a doctor, and some you can order on your own. We list each of them below along with their price and rates of accuracy. But first, five things patients need to know before getting an Alzheimer’s blood test.

1. Alzheimer’s blood tests can’t give you a definitive Alzheimer’s diagnosis

These blood tests are not designed to diagnose Alzheimer’s disease. They detect the levels of proteins in the blood that are linked to Alzheimer’s pathology in the brain. The blood test is intended to be one tool in a battery of testing that medical professionals use alongside cognitive testing and a patient’s medical history to make an accurate diagnosis.

So, if you test positive on one of these blood tests, it means that you might have a buildup of beta-amyloid plaques in the brain. If you have symptoms, it can help a doctor figure out if the symptoms are caused by Alzheimer’s or rule it out. 

But if you’re asymptomatic, it isn’t clear what the results will mean. Having Alzheimer’s pathology in the brain doesn’t mean you’ll develop Alzheimer’s disease. Upon brain autopsy, scientists have found that some 20 percent of cognitively healthy older adults also have a lot of buildup of these proteins in the brain. 

2. Getting one of these blood tests could affect insurance coverage

While there are some laws in place that prevent genetic discrimination — for example, insurance companies cannot deny general coverage to people with Alzheimer’s risk genes like APOE4 — there are no such laws for biomarkers. 

Claire Erickson, PhD, who researches medical ethics and health policy at the University of Pennsylvania, told Being Patient that there is very little protection. Tests that are direct-to-consumer have even less protections, she explained, as the information isn’t protected by general health privacy laws.

Erickson said that the accessibility of direct-to-consumer tests is “going to open a can of worms that I don’t think that we’re prepared for,” she said. She also worries that insurance companies in the future might ask people for their Alzheimer’s biomarker status before deciding whether to grant long-term care insurance. In a 2023 research article, Erickson and colleagues highlighted the need for new laws to prevent discrimination.

3. Doctors still need to be part of the process

Most of the blood tests on the market are ordered by a doctor or neurologist. When the results come in, they can guide patients and explain exactly what it means to test positive on a certain test in the context of your symptoms and medical history. This help patients feel less anxious about the results and helps them understand that a positive test does not mean Alzheimer’s disease.

But with Quest Diagnostics, and other companies that may market tests as “direct-to-consumer” tools, experts agree, the idea goes off the rails. The test is too widely available as it is, neurologists and healthcare providers agree — and as for the barriers to entry that are in place, they are not going to be easy to enforce. To ensure the test is only taken by eligible parties, Quest asks buyers to click a check-box prior to checkout — as one would see in standard “terms of service” agreements — saying they meet the criteria. 

There’s no safety net if you order an Alzheimer’s test yourself. The advantage of going through the doctor is that they are available to answer any questions or uncertainties that arise.

4. So far, the tests aren’t standardized — and results will…