Much Ado About Blood Test for Alzheimer's Disease

Contributed by: Dennis Fortier, President, Medical Care Corporation

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The general press is widely reporting today on a blood test for predicting Alzheimer's Disease (AD). The media coverage is based on a study conducted at Georgetown University Medical Center and published in Nature Medicine. Despite the intense focus, there really may be very little news in this story.

It is unclear why CNN would report this as a "first-of-its-kind" study, when dozens of such studies have been presented and published over the last decade (we wrote in this space about one from Johns Hopkins and another from Scripps). Past studies have been based on various, different elements in the blood but have, in some instances, shown similar levels of predictive accuracy. This study was certainly among the most accurate, but even these results need to be considered in the context of how AD progresses

In terms of AD progression, there seems to be a fairly low level of appreciation, among health reporters, about the underlying nature of the disease. To suggest that we can somehow predict sudden and stark symptoms that mark the beginning of AD, is to ignore decades of research showing that pathological changes associated with the most common forms of the disease, progress slowly for decades before damaging the brain enough to produce symptoms. At best, this new blood test might give insight that a person is in that long, variable process. But bear in mind, autopsy data show that nearly everyone has AD pathology in the brain after age 65, though most do not have any AD symptoms. Therefore, a test to detect what we currently believe to be the pathology, just isn't yet very informative.

Furthermore, a new blood test that suggests those pathological changes are underway is great, but physicians can already detect such murky signs in many ways (MRI scan, spinal tap, PET Scan, etc.). Blood tests have general advantages in terms of cost and convenience, so the reported accuracy of this test is certainly a welcome step forward. But it probably doesn't provide a lot of new insight about whether or not  a person is progressing toward the symptomatic stage of AD.

Finally, the fervor from the ethicists about the moral dilemmas associated with AD diagnoses, is misplaced. If some society wants to make a universal decision about whether or not every citizen should or should not have access to such tests, then the ethicists should weigh in. In our society, where people can decide for themselves if they wish to see a doctor and complain about a symptom, there really is no moral dilemma: those who want information will seek out such tests, and those who do not, will not.