Clinical, Cognitive, and MRI Profiles in a Memory Clinic Cohort with Negative Versus Positive PET Amyloid Scans
Bibliographic record
Abstract
BACKGROUND: . Understanding the cognitive and MRI features that distinguish amyloid-negative from amyloid-positive patients is essential for refining diagnostic accuracy METHOD: This descriptive study included 56 patients with cognitive complaint (28 amyloid-PET- negative, 28 amyloid -PET-positive) who were evaluated between 2023 and 2025 at the UHN Memory Clinic and had a positron emission tomography (PET), MRI and Toronto Cognitive Assessment (ToRCA). Demographic, cognitive, amyloid PET scan and MRI data were compared, with medians and interquartile ranges (IQR) reported for non-normally distributed variables. RESULT: Both groups had similar age (70.0 [65.5-76.8] vs. 74.5 [66.0-78.0], p = 0.768) and sex distribution (57.1% male, p = 1.000). Amnestic MCI was more frequent in the amyloid-negative group (89.3% vs. 57.1%, p = 0.016), while dementia was more common in the amyloid-positive group. Amyloid-negative patients showed better delayed recall (3.00 [2.75-5.00] vs. 1.00 [0.00-3.25], p = 0.008), delayed recognition (19.00 [16.00-20.00] vs. 17.00 [12.00-18.00], p = 0.006), and visuospatial memory (Benson Figure Delayed Recall: 10.00 [8.00-12.00] vs. 8.00 [3.00-10.25], p = 0.021) than the amyloid-positive group. Semantic fluency (animals) was also higher (16.00 [12.00-18.25] vs. 13.00 [7.75-15.25], p = 0.006) in the amyloid-negative patients, while lexical fluency (F words) was comparable (p = 0.134). There were no significant differences in global cortical atrophy or moderate-to-severe atrophy of the medial temporal lobes. CONCLUSION: This descriptive study suggests that amyloid-negative patients are more likely to present with aMCI than dementia, and exhibit milder memory deficits than amyloid-positive patients, aligning with reports that LATE may be less severe than AD. Though referral bias may partly explain the higher proportion of aMCI in the amyloid-negative group, these findings underscore the need to consider non-AD pathologies in patients with memory complaints and negative amyloid scans. Future research may elucidate distinct clinical signatures to improve diagnostic workflows in memory clinics.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".