A blood test can diagnose if you’ll get Alzheimer’s. Would you take it?

Investigators reported that they’ve developed a blood test that can diagnose Alzheimer’s disease. It’s pretty accurate, and it may allow someone to know if he’s at high risk to develop Alzheimer’s years before the symptoms become manifest.

But is it too much information?  Would you take the test?

What is Alzheimer’s?

Alzheimer’s is a neurodegenerative (causes the destruction of neurons [brain cells]) disease that is the leading cause of dementia.  It is also fatal.

Dementia is a deterioration of cognitive abilities such as memory loss, decreased ability to concentrate loss of good judgment. It can also cause personality changes and emotional disturbances. Patients with Alzheimer’s develop dementia. Dementia can be caused by other diseases as well such as: tumors, strokes, Parkinson’s disease, head trauma and others.

Older couple via Shutterstock

Older couple via Shutterstock

Over 5 million Americans have Alzheimer’s disease. This disease can often start insidiously and gradually worsen. The patient will need more and more assistance. He may start off just needing the occasional reminder. Later he may not only need reminders, he may need help with some tasks: eating, bathing, using the bathroom and others. Eventually, he may need 24/7 care.

The time from diagnosis of Alzheimer’s (using clinical examination to look for when the first signs are apparent) to the patient’s death is on the order of 5-10 years.

The diagnosis of Alzheimer’s till now could only definitively be done through doing a brain biopsy or, after death, by examining the brain at autopsy. So until now, the diagnosis of Alzheimer’s was made by eliminating (“ruling out”) other causes of dementia. If nothing else was causing the dementia, then Alzheimer’s was the culprit.

Some forms of dementia are treatable and may improve. This isn’t the case with Alzheimer’s. In spite of using the few available medications, the disease progresses and the patient eventually dies. Death from Alzheimer’s ranks in the top ten causes of death in the US.

Diagnosing Alzheimer’s

When brain cells die, they burst and their contents are scattered locally. The contents of the cell and its membrane are proteins, lipids and carbohydrates and some other components. Quantities of those substances find their way into the blood. Some of the proteins are fairly unusual and not normally seen in the serum in significant quantities. Some may cause an immune response where antibodies directed against these proteins are formed. Work going back several years showed that some of those proteins might be useful to predict if a patient had a higher risk for getting Alzheimer’s.

Other scientists focused on the lipids (fats) released from the cell and cell membrane. This lipid research was just recently released. Again, some of those lipids aren’t commonly encountered in significant quantities in the blood of patients who aren’t going to develop Alzheimer’s (i.e., those who don’t have neurodegenerative disorders.)  If the test is positive, it may be years till the first signs of dementia are noted, and more years before the disease progresses to severe impairment and then death.

Investigators feel that, perhaps, there hasn’t been much success in treating Alzheimer’s disease because treatments start too late. That is, the patient isn’t diagnosed until he is showing significant signs of dementia. The thought is, that with earlier diagnosis, current treatment methods might be more effective. And, perhaps, by studying these patients before Alzheimer’s becomes too far advanced, additional insights on the mechanism and treatment of the disease might be found.

Would you want to be tested? Would you want to know?

But now an interesting question arises. Since the test detects a disease that is progressive, incurable and invariably leads to death, would you want to be tested?

Knowing all that a positive result implies, would you want to know if you’re positive or negative?

I’m sure that some people would, and others wouldn’t, want to be tested. Since there’s a genetic predisposition to Alzheimer’s, would your choice on whether to be tested be affected by a family history of Alzheimer’s?  And if so, would the family history make you more or less likely to be tested?

There may be an association between head trauma and Alzheimer’s. And a link between cardiac health and the development of Alzheimer’s. So if you had head trauma in the past, would you be more interested in your risk? An alternate option is to have the test done, but don’t get your results. Let your doctor have them. He can keep the results secret from you but keep a closer eye on you for signs of dementia if the test is positive.

This question of testing doesn’t just hold for Alzheimer’s. There are other diseases that are progressive and incurable — Huntington’s disease (formerly Huntington’s chorea) comes to mind for one.  So it’s a much larger question that we may be facing more and more as science advances.

So, it’s your choice – to test or not to test. Which would you choose?  Feel free to weigh in via the comments, I’ll join you there in a bit.

Mark Thoma, MD, is a physician who did his residency in internal medicine. Mark has a long history of social activism, and was an early technogeek, and science junkie, after evolving through his nerd phase. Favorite quote: “The most exciting phrase to hear in science... is not 'Eureka!' (I found it!) but 'That's funny.'” - Isaac Asimov

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