Medial temporal tau can be a predictor for amyloid-ß positivity in mild cognitive impairment

Abstract Introduction Although both amyloid-ß (Aß) and tau positron emission tomography (PET) are important for the assessment of Alzheimer’s disease pathology, obtaining two PET scans can be challenging in clinical practice. We sought to determine whether Aß-positivity in MCI patients can be predicted with only a single tau PET scan. Methods We prospectively recruited 105 MCI patients and performed two PET scans with 18 F-florbetaben and 18 F-flortaucipir with all patients. Regional 18 F-flortaucipir standardized uptake value ratios (SUVR) were measured using FreeSurfer-generated volumes-of-interest and with the cerebellar crus median as a reference. Results We classified 49 (46.7%) MCI patients as Aß-positive using visual assessment. In 12 regions showing greater tau uptake in the MCI-Aβ+ patients compared to the MCI-Aβ- patients, tau uptake in the entorhinal cortex showed the greatest area under the curve (AUC) value (AUC = 0.835, sensitivity/specificity = 73.5% /85.7%) for discriminating Aß-positivity. The second and third largest AUCs were obtained with tau uptake in the amygdala (AUC = 0.814, sensitivity/specificity = 65.3%/94.6%) and the parahippocampal cortex (AUC = 0.802, sensitivity/specificity = 67.4%/91.1%). However, post-hoc analyses revealed no statistical differences between the three regions. Conclusions Single tau PET scans may be helpful in the evaluation of disease state and stage at the same time in MCI patients.