Abstract
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Objectives To assess the diagnostic value of [11C]Pittsburgh compound-B (PIB) and [18F]fluorodeoxyglucose (FDG) PET in a memory clinic setting.
Methods Paired dynamic (90 minutes) PIB and static FDG (15 minutes) PET scans were performed in 154 patients, shortly after completing a standard dementia work-up. PET images were visually assessed by a nuclear medicine physician and reported to the cognitive neurologists. Outcome measures were (change in) clinical diagnosis and confidence in that diagnosis after disclosing PET results.
Results At baseline, patients were diagnosed with Alzheimer’s disease (AD, n=66), mild cognitive impairment (MCI, n=30), subjective memory complaints (n=15), frontotemporal dementia (FTD, n=18), dementia with Lewy bodies (n=5), other forms of dementia (n=10), and other psychiatric (n=6) or neurological diseases (n=4). PIB scans were positive in 40/66 patients with clinical AD (61%) and 5/18 patients with clinical FTD (28%). FDG uptake patterns matched the clinical diagnosis in 58% of patients with clinical AD, and in 33% of patients with clinical FTD. PET results led to a change in diagnosis in 35 (23%) patients. A change in clinical diagnosis only occurred when diagnostic certainty was lower than 90% prior to PET. Furthermore, percentage diagnostic alterations after PET increased with decreasing pre-PET diagnostic certainty. Diagnostic confidence increased from 71±17% before to 87±16% after PET (p<0.001). Two year clinical follow-up in a subsample (n=39) showed that PIB and FDG predicted progression to AD for patients with MCI, and that the diagnosis of dementia established after PET remained unchanged in 96% of the patients.
Conclusions PIB and FDG are of additional value over the standard diagnostic work-up in a memory clinic setting. Molecular imaging is certainly useful for establishing an early (prodromal) diagnosis of AD and for differentiating between specific dementias, especially when prior diagnostic certainty is low.
Research Support Center for Translational Molecular Medicin