PET Amyloid Ligand [<sup>11</sup>C]PIB Uptake and Cerebrospinal Fluid β-Amyloid in Mild Cognitive Impairment

Abstract

BACKGROUND: In mild cognitive impairment (MCI), Alzheimer's disease (AD)-type cerebrospinal fluid (CSF) biomarker profiles predict rapid progression and conversion to AD. An increased brain amyloid burden in AD and MCI has been demonstrated with PET using [(11)C]PIB (Pittsburgh compound B). Little is known about the relationship between these biomarkers in MCI. METHODS: We studied 15 patients with amnestic MCI and 22 controls with PET using [(11)C]PIB. In MCI patients, CSF levels of Abeta42, pTAU, totalTAU and the Abeta42/pTAU ratio were measured. RESULTS: In MCI patients, CSF Abeta42 was abnormal in 53% of patients, totalTAU in 67%, pTAU in 64% and the Abeta42/pTAU ratio in 64%. A composite neocortical [(11)C]PIB uptake score was increased in 87% of the MCI patients. Only 54% of [(11)C]PIB-positive subjects showed AD-type Abeta42 values. During a 2-year follow-up, 6 MCI patients converted to AD, all of them had increased neocortical PIB scores at the MCI stage. Abnormal CSF Abeta42 was found in 3 patients, pTAU in 3 patients and Abeta42/pTAU ratio in 4 patients. CONCLUSION: Follow-up studies are needed to confirm whether [(11)C]PIB uptake might be more sensitive than CSF Abeta42 concentration in detecting increased amyloid burden in MCI, as suggested by the results of this study.