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DISCREPANCIES BETWEEN PIB AMYLOID IMAGING IN TYPICAL AND ATYPICAL CLINICAL DIAGNOSIS: PRACTICAL UTILITY IN A MEMORY CENTER

      Background: The 11C-PIB-PET is a tracer that specifically detects amyloid deposition in life. It has the advantage of being minimally invasive, but it is expensive and its use care in the clinical spectrum of degenerative diseases has not been stipulated. Our goal is to determine the utility of 11C-PIB-PET analyzing the presence of amyloid in patient groups high and low pretest probability.
      Methods: Observational cross-sectional study 144 patients underwent 11C-PIB-PET in our center. They were assigned into categories of high or low pretest probability according to clinical suspicion of AD pathology. The high probability group included: mild cognitive impairment (MCI), amnestic, amnestic and other domains MCI, Alzheimer disease (AD), posterior cortical atrophy (PCA), logopenic Primary Progressive Aphasia (PPA), amyloid angiopathy and mixed dementia. The low assumption group included: normal controls, non-amnestic MCI, non logopenic PPA and frontotemporal dementia (FTD).
      Results: 29.67% of patients with high pretest probability had 11C-PIB-PET negative, and 26.42% in the low-probability was positive. The syndromic diagnoses that most discrepancies were found were: amnestic MCI (37% had negative PIB), amnestic and other domains (40%, negative PIB) into high probability group; non-amnestic MCI (33% positive PIB), and non-logopenic PPA and FTD (33% and 45% positive PIB) into low probability group. Normal controls and AD patients (typical and atypical presentation) were the most consistent across clinical and molecular diagnostics.
      Conclusions: There were discrepancies in molecular diagnosis in both high and low probability groups. The implications of these inconsistencies were different between each clinical category. The most important contribution to the diagnosis of 11C-PIB-PET is really significant in cases of early-onset AD, and atypical presentation (PPA, FTD and PCA).