Semi-quantitative tau PET approaches for Braak staging: concordance of CenTauRz and STOC with visual assessment

The progression of tau pathology in Alzheimer's disease (AD) is closely linked to cognitive decline. Visual Braak staging of tau PET reflects neurofibrillary tangle distribution but requires expertise in interpretation. The present study aimed to evaluate agreement between Braak stages and semi-quantitative CenTauRz and Simplified Temporal-Occipital Classification (STOC).

We collected data from 112 persons with normal cognition (NC), as well as 103 patients with mild cognitive impairment (MCI), and 48 with AD who were assessed by ¹⁸F-flortaucipir PET and MRI in the ADNI3 study. A board-certified nuclear medicine physician visually assessed Braak stages on PET images. CenTauRz scores were derived by converting standardized uptake value ratios (SUVRs) from five predefined regions. STOC stages was based on SUVRs from four regions, and classified cognitive impairment into five stages of typical tau progression or atypical patterns. Tau positivity was defined as Braak stage ≥ IV, CenTauRz ≥ 2.0, or STOC stage ≥ 2/atypical. Concordance (Cohen's κ) and Spearman's correlations (rho, ρ) with Braak stages were calculated.

The accuracy of CenTauRz compared to Braak stages was 0.84-0.90, κ = 0.61-0.77, and ρ = 0.67-0.83 and that of STOC was 0.87; κ = 0.71, and ρ = 0.81. CenTauRz captured the regional heterogeneity of tau accumulation, whereas STOC provided a staging framework aligned with Braak progression.

The agreement of CenTauRz and STOC with visually assessed Braak stages was strong. Combinations of semi-quantitative methods might serve as complementary tools for tau PET images and improve interpretive reliability and objectivity.