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

<i>Background:</i> 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 [¹¹C]PIB (Pittsburgh compound B). Little is known about the relationship between these biomarkers in MCI. <i>Methods:</i> We studied 15 patients with amnestic MCI and 22 controls with PET using [¹¹C]PIB. In MCI patients, CSF levels of Aβ42, pTAU, totalTAU and the Aβ42/pTAU ratio were measured. <i>Results:</i> In MCI patients, CSF Aβ42 was abnormal in 53% of patients, totalTAU in 67%, pTAU in 64% and the Aβ42/pTAU ratio in 64%. A composite neocortical [¹¹C]PIB uptake score was increased in 87% of the MCI patients. Only 54% of [¹¹C]PIB-positive subjects showed AD-type Aβ42 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 Aβ42 was found in 3 patients, pTAU in 3 patients and Aβ42/pTAU ratio in 4 patients. <i>Conclusion:</i> Follow-up studies are needed to confirm whether [¹¹C]PIB uptake might be more sensitive than CSF Aβ42 concentration in detecting increased amyloid burden in MCI, as suggested by the results of this study.