Test for Alzheimer’s possible

WASHINGTON – It’s a cruel disease, stealing away personality and bringing heartbreak to families as they watch the joy of shared memories fade from a loved one.

As many as 4 million Americans may suffer from Alzheimer’s. But it’s impossible to make a diagnosis for sure – until after death.

That poses severe obstacles for researchers trying to find treatments at the earliest stages of the disease.

A supersensitive new test may offer hope – not of a cure yet, but that the disease can be detected early so therapies can be tried and maybe a treatment found.

It is important to have some way to diagnose the disease while the patient is still alive, especially during its early stages, so experimental treatments can be evaluated, and to catch it at a time when the disease might be treatable.

“If you can’t diagnose it, you’re not going to have a therapy for it,” said Chad Mirkin of Northwestern University.

Many companies have experimental therapies, he said.

“But those therapeutics aren’t very good if you can’t definitively diagnose and follow a disease,” explained Mirkin, a lead researcher – along with William Klein – on a team that developed the new test, which can detect small amounts of proteins in spinal fluid.

The team’s findings are reported in today’s issue of Proceedings of the National Academy of Science.

The test, called a bio-barcode assay, is 100,000 times to 1 million times more sensitive than other available tests, Mirkin said in a telephone interview.

It was first used last year in testing for a marker for prostate cancer, and Mirkin said he invited other investigators to suggest subjects for further testing

Klein, also at Northwestern, had done research associating Alzheimer’s with a protein in the brain called amyloid-beta-derived diffusible ligand, or ADDL, Mirkin said.

So the research team set out to try and detect ADDL in spinal fluid.

They got samples of the spinal fluid of 30 people, 15 who had Alzheimer’s disease and 15 who did not.

The researchers found at least some ADDL in all the patients, which Mirkin said is an indication that everyone may have a baseline level of the protein.

The method needs to be repeated and tested on more patients, he said. Also, tests need to be done to see if high levels of ADDL occur in other memory-loss diseases.

But, the researchers said in their paper, the work provides a “potential reliable detection method for diagnosing” Alzheimer’s disease.

In addition, Mirkin said, the researchers are hoping to use the new test to search for proteins and other chemicals that can offer early diagnoses of other diseases ranging from cancers to AIDS to mad cow.

The research was funded by the National Science Foundation, Nanoscale Science and Engineering Center and the National Institutes of Health.