Findings to be presented by Avid's founder (right) Dr  Daniel Skovronsky at an international Alzheimer’s Association in July still needs Food and Drug Administration confirmation and approval, but it seems for the first time doctors will have a reliable diagnostic for the presence of Alzheimer’s in living patients with memory problems.

There is no treatment yet to stop or slow Alzheimer progress. Major drug company have new experimental drugs hoped to work, if started early. But who should get these? Who has Alzheimer? Who is developing it?

High rate of misdiagnosis
Some 20% of those with memory or intellectual memory loss - dementia - diagnosed with Alzheimer’s, do not have it. There is no plaque on biopsy. Around 50% with mild memory loss and thought to be developing Alzheimer’s, do not get the disease.  A  high rate of misdiagnosis means some are not treated for conditions like depression or low levels of thyroid hormone or drug side effects and interactions that are causing their specific memory problems and are not Alzheimer related.

Early this decade, (left) Chester Mathis and William Klunk (right) the scientists at University of Pittsburgh developed an amyloid dye that while not practical for widespread use, showed it was possible to see amyloid in a living brain.

Work with collaborators in Sweden to test their dye in humans in 2002, found  the PET scan had showed amyloid exactly where it had been  expected and then no plaque signs in PET scan and an autopsy showing no presence of Alzheimer’s.

But was a PET scan with the Pittsburgh dye really as true as a brain autopsy? Skovronsky vworked with University of Pennsylvania chemist, Hank Kung  (left) for nine years to find and develop their radioactive dye.

They took the approach to use fluoride 18, with a half-life of about two hours. It could be made in the morning, and used tin the afternoon. Fluoride 18 is made routinely for 2m cancer PET scans each year. The university held the patent, so Avid licensed it and planned to make hospice patients study subject.

Some with dementia, some without, all would have memory tests and brain scans. After death the autopsies of the first 35 to die  should present be enough data to know if the scans gave a true picture of the pathology. Then the F.D.A. could decide if the results were convincing enough to approve the dye for marketing.

Despite some misgivings most patients and families agreed and said they were grateful to have been asked. The first six scans gave encouraging results. The Avid study was completed in May.

The anomolous 20%
Mostly the scans were as expected — those with Alzheimer’s had lots of plaque, those with normal memories had little if any and those with mild memory impairment were in between. But a new finding sees that 20% of people over 60 with normal memories, also have plaque.

“The 20% who had amyloid, though they were still statistically in the normal range, did worse on every memory test than the control group,” noted Dr. Skovronsky. "Were they starting to develop Alzheimer’s? If so, could dementia be stalled if there were drugs to stop amyloid from accumulating?"

The definition of Alzheimer’s is plaque plus memory loss and other symptoms of mental decline. But what is not known, because no one could follow the development of plaque before a person died, was whether people with plaque and normal memories were developing Alzheimer’s.

Dr. Steven T. DeKosky, an Alzheimer’s researcher, VP and dean at the University of Virginia School of Medicine notes “We never had a way to detect plaque in living persons,” Plaque in the brains of people with normal memories has been a puzzle. “Over the next couple of years, we will find out what it means.”