One stop shop: Flortaucipir PET pattern predicts amyloid positivity in neurodegenerative diseases

Objectives: Intraneuronal aggregation of tau proteins are a hallmark of cerebral pathology in the two of the most common forms of neurodegenerative dementia (ND): The amyloid-associated (amy+) Alzheimer’s disease (AD) and the non-amyloid associated (amy-) fronto-temporal lobar degeneration (FTLD). In recent years, Flortaucipir and other tau PET tracers have been developed and are being evaluated. This study investigates the ability of Flortaucipir PET to reliably differentiate amy+ and amy- forms of ND.

Methods: 35 patients with amy+ and 19 patients with amy- forms of ND underwent Flortaucipir PET. PET data were subject to a purely data-driven scaled subprofile modelling/principal component analysis (SSM/PCA; Eidelberg et al. Trends Neurosci 2009) to identify spatial covariance patterns. SSM/PCA components were tested for their ability to differentiate amy+ from amy- patients by measuring individual pattern expression strengths. Thresholds were defined by a receiver operating characteristic (ROC) analysis and validated with a leave-one-out approach.

Results: The expression of the main (first) SSM/PCA component separated groups with a sensitivity of 0.97 and a specificity of 0.90, (AUC = 0.97). Anatomically, group separation performance was driven by parietooccipital grey matter binding (amy+) vs. disseminated white matter binding (amy-) (Figure 1).

Conclusions: Expression strength of an SSM/PCA derived binding pattern of Flortaucipir discriminates amy+ from amy- forms of ND with high accuracy. Together with a perfusion weighted early-phase acquisition, Flortaucipir PET alone - as a one stop shop examination - may convey equivalent information to additional amyloid and FDG-PET to characterize the form of ND.

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