PET Scans with Florbetapir F 18 Help Alzheimer’s Diagnosis

Positron emission tomography (PET) combined with the tracer florbetapir F 18 showed significant differences in beta-amyloid burden in the brains of patients with probable Alzheimer’s disease, mild cognitive impairment, and healthy older adults, according to a new study published online this week in the Archives of Neurology.

The researchers, led by Adam S. Fleischer of the Banner Alzheimer’s Consortium in Phoenix, Ariz., say radiologists using florbetapir PET could thereby help diagnose Alzheimer’s disease as well as the amyloid levels of patients at risk of the disease.

Beta-amyloid is considered a key player in Alzheimer’s disease, which the Alzheimer’s Association estimates to affect 5.4 million Americans.

The study involved 68 participants with probably Alzheimer’s disease, 60 with mild cognitive impairment, and 82 healthy adults aged 55 and older. The researchers considered cerebral-to-whole-cerebellar standard uptake value ratios (SUVRs) for the three groups, and then compared mean cortical SUVRs. An SUVR greater than or equal to 1.17 reflected beta-amyloid levels of Alzheimer’s disease. A separate set of 19 Alzheimer’s patients who underwent PET and postmortem examinations had established this. Similarly, a threshold SUVR of 1.08 was used to establish the presence of beta-amyloid based on a separate set of 46 individuals 18 to 40 years of age.

Patients with Alzheimer’s disease had mean cortical florbetapir SUVRs of 1.39; those with mild cognitive impairment were at 1.17, and the control group registered 1.05. On a percentage basis, 80.9 percent of the suspected Alzheimer’s group met the amyloid threshold associated with Alzheimer’s disease, with 46.6 percent of those with mild cognitive impairment and 28.1 percent of the control group reaching those amyloid levels.

The authors said their study confirms the ability of florbetapir PET to characterize amyloid levels in probably Alzheimer’s disease patients, those with mild cognitive impairment, and healthy adults.