Equivocal vs Positive Technetium-99m-Pyrophosphate Scintigraphy for Transthyretin Amyloid Cardiomyopathy: Comparing Outcomes, Demographics, and Imaging
Bibliographic record
Abstract
Background: Transthyretin cardiac amyloidosis (ATTR-CM) is an underdiagnosed infiltrative cardiomyopathy. Diagnosis is based on Technetium-99m-pyrophosphate-bone-scintigraphy scans (Tc-99m-PYP) with grades 2 to 3 classified as positive. The clinical significance of grade 1 (classified equivocal by American Society of Nuclear Cardiology) is unclear. We aimed to describe the differences in clinical/imaging characteristics among those with equivocal vs positive Tc-99m-PYP and to describe outcomes of further investigations. Methods: We performed a retrospective study of patients who underwent Tc-99m-PYP at 2 institutions between January 2017 and November 2022. Baseline demographics, laboratory, and imaging data were collected. Results: A total of 502 Tc-99m-PYP were performed with single-photon emission computed tomography (SPECT) 3 hours post-tracer injection: 347 (69%) negative, 46 (9%) equivocal, and 109 (22%) positive. In the latter 2 groups, the median age was 78 (interquartile range [IQR]: 72-84) years, and 38 (25%) were female. Average follow-up was 19.7 ± 14.6 months. No patients with equivocal scans were diagnosed with ATTR-CM. Equivocal scans had lower intraventricular septal diameters (11 mm [IQR: 10-11] vs 15 mm [IQR: 12-17]), larger left ventricular end-diastolic dimension (50 mm [IQR: 44-56] vs 43 mm [IQR: 40-50]), and more negative global longitudinal strain (-18.7 [IQR: -22.2 to -18.7] vs -13.8 [IQR: -17.9 to -10.9] %). Only 12 (26%) patients with equivocal scans underwent further imaging or biopsy. Of 2 patients with monoclonal gammopathy, 1 had AL-amyloidosis. Conclusions: Our patients with equivocal grade 1 scans were not diagnosed with ATTR-CM. They exhibited distinct imaging compared to positive scans. Our findings suggest that ATTR-CM phenotype and equivocal scans may represent early ATTR-CM (ie, false negative) or false positives and should undergo further workup. Further research is needed to determine the significance of equivocal studies.
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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 | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".