Background and Objectives Early dementia risk-stratification is crucial for timely intervention. Brain-predicted age difference (brain-PAD) derived from structural MRI reflects the gap between computer-estimated age and chronological age and has been linked to clinical progression to dementia. We evaluate whether brain-PAD has prognostic value for progression to dementia in subjective cognitive decline (SCD) and mild cognitive impairment (MCI) and whether brain-PAD provides added value beyond visual rating scales. Methods This retrospective cohort study included patients with SCD and MCI with up to 10-year follow-up assessments from the Amsterdam Dementia Cohort and SCIENCe project. Brain-PAD was computed from baseline MRI using 2 pretrained methods. Cox proportional hazards models assessed the association between brain-PAD and risk of progression to dementia, controlling for age, sex, Mini Mental State Examination, and visual rating scales. We tested interactions between brain-PAD and baseline diagnosis to assess stage-specific value and evaluated the added value beyond amyloid status in a biomarker-available subset. Results The study included 799 patients (SCD 412, MCI 387; 39.4% female, 63.3 ± 8.0 years). During a median follow-up of 3.2 years, 235 (29.4%) progressed to dementia. Higher brain-PAD was associated with an increased risk of progression to dementia (hazard ratio [HR] 1.04, 95% CI 1.02–1.06) and improved model fit beyond visual ratings (χ2 = 12.24, p = 0.003). Following a significant interaction between brain-PAD and baseline diagnosis (p = 0.013), stratified analyses demonstrated brain-PAD was a stronger predictor in SCD (HR 1.09, 95% CI 1.03–1.15) than in MCI (HR 1.01, 95% CI 0.99–1.04). In SCD, brain-PAD improved model fit beyond visual rating scales (χ2 = 10.17, p = 0.003) and modestly increased discrimination (C-index +0.02). A data-driven brain-PAD cutoff of −2.6 years corresponded to a high negative predictive value (0.91–0.99) over 2–10 years. Although brain-PAD improved model fit beyond amyloid status (χ2 = 6.44, p = 0.018), it did not improve discrimination. In MCI, brain-PAD provided no additional value (χ2 = 0.88, p = 0.351). Discussion MRI-derived brain-PAD predicts progression to dementia in memory clinic patients with SCD or MCI. In particular, brain-PAD provided additional predictive value to visual rating scales in patients with SCD.
Stefan de Vries, Katalin Farkas, H. Rhodius-Meester et al.· Neurology· 0 citations
Importance
Amyloid positron emission tomography (PET) is increasingly used in research and clinical settings to determine the etiology of cognitive decline and eligibility for amyloid-targeting therapies. To assist with amyloid PET evaluation and to guide clinical decision-making, images can be quantified in a standardized unit called Centiloid, the interpretation of which can vary according to the method and threshold used.
Objective
To collect Centiloid values from available studies and determine robust positivity cutoffs using data-driven methods and correspondence with visual reads.
Data Sources
PubMed search (October 2024) identified studies with Centiloid values. Corresponding authors were invited to share individual participant data. Additional data were obtained through access-controlled repositories and conference outreach (July 2024-July 2025).
Study Selection
Studies were included if they provided Centiloids, radiotracer, age, and sex.
Data Extraction and Synthesis
Each study was analyzed using a unified statistical pipeline; study estimates were pooled using random-effects meta-analysis.
Main Outcomes and Measures
Gaussian mixture models (GMMs) were fitted to Centiloid values for each study. In studies with a bimodal distribution (per integrated completed likelihood), single cutoffs for positivity were set as mean plus 2 SDs of the lower gaussian component. Using GMMs, a double-cutoff approach defined a lower certainty range using a 90% posterior probability cutoff for assignment to the low (amyloid-negative) vs high (amyloid-positive) component. An alternative Centiloid cutoff was derived from maximizing the correspondence (Cohen κ) with the binary visual reads when available.
Results
This meta-analysis included cross-sectional amyloid PET scans acquired with 5 radiotracers from 49 227 participants across 53 studies from 15 countries (mean age, 71 years; 54% female, 62% cognitively impaired). The data-driven GMM approach identified a bimodal distribution in 51 studies (n = 48 786), resulting in a single cutoff for positivity of 18 Centiloids (95% CI,16-19; I2 = 97%). The double-cutoff approach revealed high confidence for interpreting scans as negative when Centiloid values were lower than 11 (95% CI, 9-13; I2 = 95%) and interpreting scans as positive if Centiloid values were higher than 26 (95% CI, 24-28; I2 = 95%). In analyses of correspondence with binary (positive or negative) visual reads of amyloid PET scans (n = 35 045; 36 studies), Centiloids were highly predictive of visual positivity (Cohen κ, 0.86; 95% CI, 0.83-0.89; I2 = 96%) with a cutoff of 27 Centiloids (95% CI, 24-30; I2 = 80%).
Conclusions and Relevance
In this individual participant data meta-analysis, positivity cutoffs converged around 18 Centiloids (data-driven) and 27 Centiloids (visual reads). Findings from a double-cutoff analysis suggest that scans in the 11 to 26 Centiloid range should be interpreted with caution depending on the context of use.
Ganna Blazhenets, David N Soleimani-Meigooni, Konstantinos Chiotis et al.· Journal of the American Medi...· 2 citations
