PiB as antecedent biomarker of Alzheimer's disease

Objectives In-vivo amyloid imaging longitudinal studies enable researchers to more clearly define the role of Aβ deposition in the development of dementias where Aβ may play a role.

Methods 120 subjects -34 with Alzheimer’s disease (AD), 42 with Mild Cognitive Impairment (MCI) and 44 age-matched healthy controls (HC) - were re-assessed 18-42 months (mean 23 months) after their first ¹¹C-PiB-PET scan. Every participant underwent a comprehensive neuropsychological examination.

Results At baseline, all AD patients showed marked PiB retention, while 26/42 MCI subjects (62%). and 16/44 HC (36%) were classified as PiB-positive. There was no significant difference in PiB retention between baseline and follow-up in the HC and MCI groups, while the AD group showed a significant, albeit small (6.2%), increase in Aβ burden. There was no correlation between changes in Aβ burden and decline in cognition. At follow-up, 73% of PiB-positive MCI had declined cognitively and met criteria for probable AD. While 31% of PiB-positive HC were reclassified as MCI or AD, only 1 (4%) PiB-negative HC was reclassified as MCI.

Conclusions Aβ burden increased slowly over two years and it did not correlate with cognitive decline. Despite this slow increase, the presence of Aβ deposits in the brain is a very strong predictor of cognitive decline and progression from MCI to AD.