PET Amyloid Ligand [ super(11)C]PIB Uptake and Cerebrospinal Fluid ss-Amyloid in Mild Cognitive Impairment

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 [ super(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 [ super(11)C]PIB. In MCI patients, CSF levels of Ass42, pTAU, totalTAU and the Ass42/pTAU ratio were measured. Results: In MCI patients, CSF Ass42 was abnormal in 53% of patients, totaFTAU in 67%, pTAU in 64% and the Ass42/pTAU ratio in 64%. A composite neocortical [ super(11)C]PIB uptake score was increased in 87% of the MCI patients. Only 54% of [ super(11)C]PIB-positive subjects showed AD-type Ass42 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 Ass42 was found in 3 patients, pTAU in 3 patients and Ass42/pTAU ratio in 4 patients. Conclusion: Follow-up studies are needed to confirm whether [ super(11)C]PIB uptake might be more sensitive than CSF Ass42 concentration in detecting increased amyloid burden in MCI, as suggested by the results of this study.