News in Contect

Blood Test to Predict Who Will Develop Alzheimer’s Disesae

A blood test given to healthy people ages 70 and older predicted with more than 90 percent accuracy who would develop Alzheimer’s disease or mild cognitive impairment (often a precursor to Alzheimer’s) within the next few years, according to a recent study in the journal Nature Medicine. The test raises hopes for developing effective treatments or preventive measures for this devastating incurable disease, which affects more than 35 million people worldwide. But it also raises ethical concerns for healthy people, patients with Alzheimer’s disease, and participants in follow-up research studies.

What is it?

The blood test measures 10 lipids associated with the development of Alzheimer’s disease and mild cognitive impairment. The lipids were identified in a five-year study of 525 healthy people ages 70 or older. Low levels of the lipids were characteristic of most of the people who had the conditions, or who went on to develop them during the study. When the researchers validated the findings by giving the blood test to 41 additional participants, they found that it predicted with more than 90 percent accuracy who would develop Alzheimer’s or mild cognitive impairment within two to three years. The test is not ready to be used in medical practice. First, it must be studied in a larger more diverse group of research participants to determine if the results are valid.

Ethical Issues

The blood test poses several ethical challenges. The immediate challenges are how to conduct research involving the test responsibly. The more long-term challenges concern the use of the blood test in medical practice to screen healthy patients to determine if they are at high risk for Alzheimer’s disease.

  • Ethically responsible research. Research is needed to validate the blood test and then, if it is validated, to use it to identify people likely to develop Alzheimer’s disease in whom potential therapies can be tested. Neuroscientists think that the best chance of developing effective treatments or preventive measures for Alzheimer’s disease is to test them in people before they develop symptoms. “Large numbers of individuals will need to be screened if research is to lead to valid results and new treatment options,” says Bruce Jennings, a senior advisor to The Hastings Center. But there are ethical concerns about the impact of screening healthy individuals in research studies. One of the biggest ethical questions is whether researchers are obligated to tell these people their test results. Do they have a right to know? Do they have a right not to know? How can they even understand the results when their meaning – and the rate of false positives and false negatives – is uncertain? “Everyone wants to find a treatment or cure for Alzheimer’s disease, but how much suffering, anguish, and unintended harm should medicine and society tolerate along the way?”
  • Ethically responsible medical practice. If the accuracy of the blood test is confirmed, it is likely to become available in doctors’ offices as a screening tool, possibly before any effective treatments are available. People will have to consider if they want to learn whether they are likely to develop one of the most feared conditions when they have no means of changing their fate. Hastings Center scholar Karen Maschke cited several specific questions: “Will people be able to opt out of such tests, or will they be mandated? Do physicians have a duty to warn family members about tests results even if the patient does not want his or her information revealed? What are the cost implications of a test that indicates ‘at-risk status,’ versus the cost of other approaches, such as examining family history?” Some bioethicists are concerned that people who test positive might want to end their lives, as was discussed in a recent post in Bioethics Forum, the blog of the Hastings Center Report.

News in context

The blood test is the latest of several tests that look for hidden biological signs – biomarkers – of Alzheimer’s disease before it causes symptoms such as memory loss. They include a brain imaging test approved for use by doctors evaluating patients which looks for the presence of amyloid plaque, a protein that builds up in the brains of people with Alzheimer’s disease. Another test, used in research settings, requires a spinal tap to look for amyloid and other proteins. The big advantages of the blood test over the other biomarker tests are that it is easy to use and minimally invasive. These advantages increase the likelihood that it will be used widely in research and medicine – and they increase the necessity for society to examine the ethical implications of tests that predict who is at high risk for Alzheimer’s disease and develop guidelines for their responsible use.

The Hastings Center has never shied away from the toughest ethical challenges faced by society.

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