NEW YORK (Reuters Health) – Increased brain amyloid load is associated with an increased risk of progression from mild cognitive impairment (MCI) to Alzheimer disease (AD), according to a report in the September 8th Neurology.

In a study involving 31 subjects with MCI, in vivo measurement of brain amyloid using 11C-PIB PET proved to be “a potential tool for providing prognostic information” on “increased risk of converting to AD,” Dr. Aren Okello from Imperial College London, London, UK told Reuters Health by email.

Because PET allows correlation of brain amyloid deposition with patient status, Dr. Okello and colleagues followed their subjects over 1 to 3 years, analyzing rates of progression to clinically probable AD in PIB-positive patients.

Altogether, there were 17 subjects with C-PIB retention at baseline. Fourteen of these PIB-positive patients, and one subject without C-PIB retention, developed AD.

The converters had higher PIB retention in all cortical brain regions, compared to those who did not progress to AD, both with and without correction for age.

Eight of the 17 PIB-positive subjects progressed to AD within a year. These individuals had higher PIB retention values in the anterior cingulate and frontal cortex than did the slower converters and nonconverters, although these differences disappeared after adjustment.

APOE epsilon 4 status was known for 17 subjects. Seven were carriers, of whom 4 were PIB-positive faster converters and 2 were PIB-positive slow converters.

“We are currently following up these amnestic MCI patients with serial 11C-PIB scans,” Dr. Okello said. “This will enable us to assess whether changes in amyloid deposition over time, if present, as measured by 11C-PIB PET may provide further prognostic information in those MCI patients who had not converted to Alzheimer disease during the initial follow-up period.”

“The importance of these findings will greatly increase if anti-amyloid strategies prove effective treatment in Alzheimer disease,” Dr. Okello added.

“The role of 11C-PIB (and similar ligands for beta-amyloid deposits) in routine clinical practice needs to be further defined, relative to other diagnostic markers of AD,” according to the authors of a related editorial.

In addition, Dr. Pieter Jelle Visser from VU University Medical Center, Amsterdam, The Netherlands and Dr. David S. Knopman from Mayo Clinic, Rochester, Minnesota write, the relation between amyloid retention and cognitive decline “in subjects without dementia with non-amnestic MCI and subjective cognitive impairment, or in subjects without any cognitive impairment, needs further study.”

Reference:
Neurology 2009;73:754-760,744-745.