Differential association of [11C]PIB and [18F]FDDNP binding with cognitive impairment

Objective: To evaluate associations of [C-11]Pittsburgh compound B(PIB) and [F-18]FDDNP with impairment in specific cognitive domains over the broader spectrum comprising cognitively normal elderly subjects, patients with mild cognitive impairment (MCI), and patients with Alzheimer disease (AD). Methods: Twelve patients with AD, 13 patients with MCI, and 15 cognitively normal elderly subjects were included. Paired [C-11]PIB and [F-18]FDDNP PET scans were performed in all subjects. Binding potential (BPND) was calculated using parametric images of BPND for global, frontal, parietal, and temporal cortex; medial temporal lobe; and posterior cingulate. Cognitive functions were assessed using a battery of neuropsychological tests. Linear regression analyses were used to assess associations of [C-11]PIB and [F-18]FDDNP binding with cognitive measures. Results: Adjusted for age, sex, and [F-18]FDDNP binding, higher global [C-11]PIB binding was associated with lower scores on the Mini-Mental State Examination, immediate and delayed recall of the Rey Auditory Verbal Learning Task (RAVLT), Visual Association Task, and Trail Making Test part B. Conversely, higher [F-18]FDDNP binding was independently associated with lower scores on immediate recall of the RAVLT. After additional adjustment for diagnosis, higher [C-11]PIB binding remained independently associated with delayed recall (standardized beta = -0.39, p = 0.01), whereas higher [F-18]FDDNP binding remained independently associated with immediate recall (standardized beta = -0.32, p = 0.03). When regional binding was assessed using stepwise models, both increased frontal [C-11]PIB and temporal [F-18]FDDNP binding were associated with memory, whereas increased parietal [C-11]PIB binding was associated with nonmemory functions. Conclusion: Increased [F-18]FDDNP binding is specifically associated with impairment of episodic memory, whereas increased [C-11]Pittsburgh compound B binding is associated with impairment in a broader range of cognitive functions. Neurology (R) 2009; 73: 2079-2085