PURPOSE: To evaluate cerebral amyloid-β(Aβ) pathology in older adults with cognitive complaints, visual assessment of PET images is approved as the routine method for image interpretation. In research studies however, Aβ-PET semi-quantitative measures are associated with greater risk of progression to dementia; but until recently, these measures lacked standardization. Therefore, the Centiloid scale, providing standardized Aβ-PET semi-quantitation, was recently validated. We aimed to determine the predictive values of visual assessments and Centiloids in non-demented patients, using long-term progression to dementia as our standard of truth. METHODS: One hundred sixty non-demented participants (age, 54-86) were enrolled in a monocentric [18F] flutemetamol Aβ-PET study. Flutemetamol images were interpreted visually following the manufacturers recommendations. SUVr values were converted to the Centiloid scale using the GAAIN guidelines. Ninety-eight persons were followed until dementia diagnosis or were clinically stable for a median of 6 years (min = 4.0; max = 8.0). Twenty-five patients with short follow-up (median = 2.0 years; min = 0.8; max = 3.9) and 37 patients with no follow-up were excluded. We computed ROC curves predicting subsequent dementia using baseline PET data and calculated negative (NPV) and positive (PPV) predictive values. RESULTS: In the 98 participants with long follow-up, Centiloid = 26 provided the highest overall predictive value = 87% (NPV = 85%, PPV = 88%). Visual assessment corresponded to Centiloid = 40, which predicted dementia with an overall predictive value = 86% (NPV = 81%, PPV = 92%). Inclusion of the 25 patients who only had a 2-year follow-up decreased the PPV = 67% (NPV = 88%), reflecting the many positive cases that did not progress to dementia after short follow-ups. CONCLUSION: A Centiloid threshold = 26 optimally predicts progression to dementia 6 years after PET. Visual assessment provides similar predictive value, with higher specificity and lower sensitivity. TRIAL REGISTRATION: Eudra-CT number: 2011-001756-12.

Department of Neurology Charles University 2nd Faculty of Medicine and Motol University Hospital Prague Czech Republic

Department of Psychology Wayne State University Detroit MI USA

GE Healthcare Amersham UK

Genetics Department Saint Luc University Hospital Brussels Belgium

Gordon Center for Medical Imaging Radiology Department Massachusetts General Hospital Harvard Medical School Boston MA USA

Institute of Experimental and Clinical Research Université Catholique de Louvain Brussels Belgium

Institute of Neuroscience Université Catholique de Louvain Brussels Belgium

Neurology Department Saint Luc University Hospital Av Hippocrate 10 1200 Brussels Belgium

Nuclear Medicine Department Saint Luc University Hospital Brussels Belgium

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