Can a blood test tell you if you’ll get Alzheimer’s? Be careful what you read online

A blood test for Alzheimer’s sounds like something many of us would want: a simple way to get answers early. That hope makes the tests easy to promote on social media. But a new Australian study found that posts often leave out the information people need to make an informed decision.

University of Sydney researchers examined 188 Facebook, Instagram and TikTok posts about Alzheimer’s blood tests. More than a third suggested the tests could be used to screen people without symptoms, despite current recommendations against routine testing in that group. Only 36% of posts included evidence to support their claims. Accounts with an explicit financial interest were more than three times as likely to promote testing for people without symptoms. These findings describe the posts the researchers examined; they do not tell us that every post about the tests is misleading. The University of Sydney

What can these blood tests actually do?

Some tests measure biological signs associated with Alzheimer’s disease. They may help specialists investigate whether Alzheimer’s is contributing to existing changes in memory or thinking. Depending on the particular test and situation, a result can help guide further assessment.

A blood test cannot, by itself, diagnose dementia or tell a healthy person with certainty whether they will develop it. A proper assessment also considers symptoms, medical history and other possible explanations. The Alzheimer’s Association’s clinical guideline addresses the use of certain blood tests as part of a full diagnostic assessment for people with cognitive impairment in specialist care. It does not recommend using them as a stand-alone answer. Wiley Online Library

Why does missing information matter?

A post saying “Find out your Alzheimer’s risk with one blood test” sounds reassuringly straightforward. It skips the difficult questions: Who is the test appropriate for? How accurate is this particular test? What could a positive or negative result mean? What happens next?

For someone without symptoms, a result could create anxiety without providing a clear prediction or a useful next step. The Sydney researchers noted that posts promoting testing for healthy people rarely discussed potential harms, including false positives and overdiagnosis. They also stressed that there is currently no evidence that screening people without symptoms provides a benefit. The University of Sydney

Five questions to ask when you see a health claim online

1. Who is the information for? Someone with concerning symptoms may need a different assessment from someone who feels well.
2. What does the test measure? A biological marker is not the same thing as a dementia diagnosis or a prediction of the future.
3. Is there a link to the research or a clinical guideline? A confident claim is not evidence.
4. What limitations are mentioned? Balanced information explains uncertainty and possible harms as well as benefits.
5. Is someone selling the test? A financial interest does not automatically make a claim false, but it is a reason to check it carefully.

If you or someone close to you has noticed persistent changes in memory, thinking, language or behaviour, start with a GP. They can consider other possible causes and arrange further assessment when needed. If you have no symptoms but are worried about your future brain health, discuss your concerns with a health professional before paying for a test advertised online. Wiley Online Library

The HEAL takeaway

New tests can be valuable. People deserve to know what a test can tell them, what it cannot tell them, and whether it is appropriate for them right now. Good brain health information should help people make decisions with confidence, without using fear to sell certainty.

Read the University of Sydney article · Read the published study