Abstract
INTRODUCTION: When cerebrospinal fluid (CSF) and positron emission tomography (PET) measurements for amyloid-beta-peptide (Aβ) related pathology are discordant, therapeutic decision-making becomes uncertain. METHODS: Using data from patients with mild cognitive impairment (n = 541) from the Alzheimer's Disease Neuroimaging Initiative, we examined baseline characteristics and longitudinal clinical outcomes in persons grouped according to normal/abnormal Aβ via concurrent CSF and PET determinations using standard cutpoints. RESULTS: Discordant groups for brain Aβ status (CSF+/PET- and CSF-/PET+) each represented about 5% of the mild cognitive impairment (MCI) population. Longitudinally, neither discordant group declined more than the CSF-/PET- group on either a memory measure or the Clinical Dementia Rating Sum of Boxes scores over a median 4 years of observation, while the CSF+/PET+ group exhibited worsening on both measures. DISCUSSION: In contrast to the clinical decline observed in the CSF+/PET+ group, persons with MCI and CSF+/PET- or CSF-/PET+ brain amyloid patterns did not exhibit incipient decline. HIGHLIGHTS: Discrepant abnormal cerebrospinal fluid (CSF) and positron emission tomography (PET) brain amyloid indicators are uncommon in mild cognitive impairment (MCI). CSF-PET discrepant persons with MCI tend to have less abnormal values initially. CSF-PET discrepant persons with MCI have a benign prognosis at 4 years.