PET with Florbetapir Predicts Cognitive Decline

A new radioactive agent used with PET imaging of the brain detects early evidence of Alzheimer’s in patients with mild decline or who are not yet showing cognitive impairment, say researchers in a study published today in the journal Neurology.

Researchers from Duke University Medical Center studied 151 patients enrolled in a 36-month multi-center test of the new radioactive agent, florbetapir, brand name Amyvid, which was approved by the FDA in April.

Patients underwent cognitive exams and PET imaging with florbetapir at the start of the study. The agent binds to amyloid plaques that characterize Alzheimer’s disease. The patients were reassessed with additional cognitive exams at 18 months and again at 36 months. Sixty-nine patients had normal cognitive function at the start of the study, 51 had mild impairment and 31 had Alzheimer’s dementia.

The researchers found that patients who had plaques and mild cognitive impairment at the start of the study worsened to a great degree when performing cognitive tests at 18 months compared to patients with no plaques at the start of the study. Twenty-nine percent of patients with plaques developed dementia, compared with 10 percent who had no plaques.

Differences were also seen among patients who had plaques at the start of the study but who showed no signs of cognitive impairment. These patients also demonstrated a mental decline at the 18-month testing mark.

“Even at a short follow-up of 18 months we can see how the presence of amyloid plaques affects cognitive function,” said P. Murali Doraiswamy, MD, professor of radiology at the university and one of the study’s co-leaders. “Most people who come to the doctor with mild impairment really want to know the short-term prognosis and potential long-term effect.”

Addressing the issue of test anxiety or concentration problems, the researchers reported that patients with negative scans reversed from minimally impaired to normal more often than did those with positive PET scans.

The data need to be verified by further research, said Doraiswamy. He also cautioned that a positive scan using florbetapir is not a diagnosis of Alzheimer’s disease.