FDA Approves First Blood Test for Alzheimer’s

The Food and Drug Administration (FDA) approved the first commercially available blood test that may help to diagnose Alzheimer’s disease. The approval of the test was hailed by some researchers as a major step forward in screening those who are 55 and older for the disease.

The test, which is called Lumipulse, and is marketed by Fujirebio Diagnostics, a Japanese firm, seeks to measure the level of two proteins, amyloid and tau, that have been associated with the development of the disease. When amyloid begins to accumulate in the brain, perhaps 20 years or more before symptoms of the disease first develop, it can form tangles in the brain, that as they increase may lead to memory impairment.

Researchers like Dr Allan Levey, director of Emory’s Alzheimer’s Disease Research Center, are excited by the development of tests like Lumipulse because of the potential they hold for an earlier diagnosis of the disease and treatment with new drugs that are useful for patients with an early diagnosis for Alzheimer’s.

“We have to make sure that a person has memory symptoms, and then we have objective evidence of memory loss before we do the advanced testing to see if the person has Alzheimer’s disease,” Dr Levey cautions. “We hope that we can identify people five to 10 years before their symptoms would have begun, and give them these same medicines, which are approved clinically for those people who already have problems.”

Until now, the most important tools specialists have had in diagnosing the disease were expensive brain imaging scans known as PET scans, and spinal taps, in which a needle is inserted in lower region of the spine to collect and screen cerebrospinal fluid for the proteins associated with the development of Alzheimer’s.

In studies that led to FDA approval, the blood test was shown to be over 90 percent accurate in helping to detect Alzheimer-related proteins in the brain. But specialists in the field caution that the test should only be considered after a clinical evaluation in which symptoms and other aspects of a medical history are evaluated.

And researchers emphasize that a blood test for Alzheimer’s as simple and as common as a test for cholesterol and other fats is farther downstream. And there are strong cautions that have appeared following the FDA approval that the accuracy of the test is not consistent among all racial and ethnic groups.

Dr. William Wu, who began his research at Emory and is now director of the Rutgers University Center for Healthy Aging Research, indicated that the predictive value of the test, that someone taking it actually has Alzheimer’s, is much higher among those who were tested who were white than those who were Black. In tests of 217 patients at Rutgers and Emory, the prediction that patients actually had the disease were 87 percent correct for whites but only 58 percent for Blacks. More research, Dr. Hu concluded, is needed.

“For Black patients, it’s a double whammy,” Hu said. “Not only will you have a harder time using these proteins in the spinal fluid to diagnose Alzheimer’s disease in Black patients, you will further reduce the detection rate by relying on the blood tests.”

Dr. Hu’s results are at variance with the study that the FDA used to approve the test. The government used a sample of 499 patients who were neurologically impaired and compared the results from the blood test with those that came from the traditional PET scan or spinal tap. In that study, the blood test was found to be almost 92 percent as accurate in catching those with Alzheimer’s.

Because the results were not 100 percent accurate, there is a risk, according to the FDA, of false positive or false negative results.

“False positive results, in conjunction with other clinical information, could lead to an inappropriate diagnosis of, and unnecessary treatment for, Alzheimer’s disease,” the FDA said. “This could lead to psychological distress, delay in receiving a correct diagnosis, as well as expense and the risk for side effects from unnecessary treatment. False negative results could result in additional unnecessary diagnostic tests and potential delay in effective treatment.”

Nonetheless, Dr. Levey believes that the blood test is a big step forward. “We can’t overlook that this is a huge, huge advance to be able to identify people in the earlier stages more rapidly, efficiently, and scale that so we can get this into public health. And secondly, for those appropriate, get them treated on these new medicines to slow the disease progression, because this new medicine only work in the very early stages.”