The US Food and Drug Administration (FDA) has approved the first diagnostic test for plaques in the brain associated with Alzheimer’s disease, the pharmaceutical firm Eli Lilly announced on 6 April. The method relies on a compound called florbetapir (Amyvid) that binds to amyloid plaques and can be imaged using positron emission tomography in living patients. It will be used to complement — not replace — current diagnostic criteria.
The technique received a lukewarm welcome by FDA advisers last year (see Alzheimer’s-disease probe nears approval). Although they heralded the potential of the technique to strengthen diagnoses — autopsies have shown that about one-fifth of the patients thought to have Alzheimer’s disease according to the standard criteria actually have no amyloid plaques, which means the diagnosis was mistaken — the panel was concerned by the wide variability in how physicians interpreted results of the florbetapir test.
Since then, Lilly has worked to improve physician education, in hopes of boosting standardization. Approval of the technique is a step forward, particularly for patients diagnosed with ‘mild cognitive impairment’, a relatively common condition that may — or may not — be a sign that Alzheimer’s Disease will develop, says Denise Park, a cognitive neuroscientist and a director of the Center for Vital Longevity at the University of Texas at Dallas. “After that diagnosis, it’s a wait-and-see for two to three years,” she says. “But if those patients had a negative florbetapir scan, there could be more confidence that they don’t have the disease.”
Meanwhile, researchers are anxious to improve prospects for treating Alzheimer’s disease by developing ways to diagnose it earlier, before behavioural symptoms develop. Park is searching for early signs of Alzheimer’s by using cognitive tests and florbetapir scans to follow more than a hundred healthy individuals as they age. “This test will ultimately play a huge role in the treatment and importantly in the diagnosis of Alzheimer’s disease before symptoms appear,” says Park. “But I don’t think we’re there yet.”