Abstract WP92: Radiologist Inter-rater Reliability of Prehospital Alberta Stroke Program Early CT Scores on a Mobile Stroke Unit
Bibliographic record
Abstract
Introduction: The computed tomography (CT) capabilities of mobile stroke units (MSUs) may facilitate prehospital triaging of patients with suspected large-vessel occlusion directly to thrombectomy-capable centers. However, little is known about the reliability of radiological interpretation of early ischemic changes on prehospital CTs. Methods: We identified all patients transported by the NewYork-Presbyterian MSU to Weill Cornell Medical Center with the diagnosis of acute ischemic stroke, transient ischemic attack, or stroke mimic between October 3, 2016 and December 31, 2017. All patients underwent noncontrast head CT on board the MSU using a CereTom® scanner. As controls, we matched these patients 1:1 by diagnosis to patients who were transported by standard ambulance and underwent noncontrast brain CT in our emergency department (ED) over the same period. Two neuroradiologists, blinded to patients’ characteristics and final diagnosis, independently calculated Alberta Stroke Program Early CT Scores (ASPECTS) on all scans. Weighted percent agreement and Cohen’s κ were used to assess inter-rater reliability, and paired t-tests were used to compare these metrics between MSU and ED scans. Results: Among 46 MSU patients and 46 ED patients, 52% had a diagnosis of acute ischemic stroke, 46% a diagnosis of stroke mimic, and 2% a diagnosis of transient ischemic attack. For ASPECTS score as a continuous outcome, the weighted inter-rater agreement was 98% for MSU scans versus 96% for ED scans (mean difference, 2%; 95% CI, -1% to 5%) and the weighted κ was 0.49 for MSU scans versus 0.54 for ED scans (mean difference, -0.05; 95% CI, -0.61 to 0.51). For ASPECTS score categorized as 0-4, 5-7, or 8-10, the weighted inter-rater agreement was 99% for MSU scans versus 97% for ED scans (mean difference, 2%; 95% CI, -2% to 7%) and the weighted κ was 0.66 for MSU scans versus 0.55 for ED scans (mean difference, 0.10; 95% CI, -0.87 to 1.08). Conclusions: In a sample of 96 patients, which limited our power to detect small differences, we found no substantial difference in the inter-rater reliability of ASPECTS scores obtained from MSU CTs versus ED CTs.
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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 | 0.012 | 0.039 |
| 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 | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".