Fig. 3.

Relationship between the NFT stage and the proportion of the population with an ‘amyloid plaque score’ of ‘none’ (PART definite), ‘low’ (PART possible), and ‘high’ (‘AD neuropathologic changes’). Comparisons with NFT stages and Aβ phases. Area chart. The percentage of the population (y value) corresponding to the NFT stage (X axis) for each category (color and label shown on each area) is proportional to the length of its projection on the Y axis. a The values shown here have been calculated from Table 1 of Crary et al. [8]. Percentage of normal cases (green) = NFT stage 0, amyloid plaque score = none. The PART area is surrounded by a dotted yellow line. Percentage of cases with PART ‘definite’ (yellow) = NFT stage > 0, amyloid plaque score = none. Percentage of cases with PART ‘possible ‘(dark yellow) = NFT stage > 0; amyloid plaque score = low. AD neuropathological changes [22] are indicated in shades of red, with a red border. The red and white cross-hatching corresponds to an area extrapolated from Table 1 of Crary et al. [8]: The diagnosis is necessarily AD neuropathological changes because NFT stages are >4 with a ‘moderate’ or ‘high’ plaque score. The blue arrow indicates the progression of Alzheimer disease neuropathological changes as we understand them in the context of the PART hypothesis: PART cases do not commonly progress to Alzheimer disease. Alzheimer disease begins with a low plaque count (or low Aβ phase) in the absence of tau pathology in the ECH. Please note that the frequency of cases with NFT stage 0 and ‘amyloid plaques’ (up to ‘numerous’ plaque score) is low in our experience (see text and [3]). It should also be emphasized that the dividing line between PART ‘definite’ and ‘possible’, and between PART ‘possible’ and AD-related changes is in Table 1 of Crary et al. [8] relies on an “amyloid plaque score” that differs from the “neuritic plaque score” recommended in the NIA–AA criteria [22] and from the Aβ phases recommended in the PART diagnostic criteria proposed in Table 2 of Crary et al. [8]. The difference between the density of neuritic plaques and of all types of Aβ deposits may be considerable. b The values shown here have been calculated from the cohort presented in Braak and Del Tredici [4]. Normal (green) = NFT stage 0, plaque score = none. The proportion of cases in the observed combination of NFT stages and Aβ phases are indicated in red shading. The blue arrow indicates the progression of the changes in the context of the continuum hypothesis defended here