Beyond Scalar Scores: Exploring LLM-based Metrics for Clinical Significance Evaluation in Radiology Reports

Qingyu Lu, Ruochen Li, Liang Ding, Yufei Xia, Youxiang Zhu, Dacheng Tao


Abstract
Automated evaluation of radiology reports is essential for clinical trust, yet clinically significant errors (e.g., missed findings or incorrect descriptions) can critically mislead diagnosis. Traditional metrics fail to distinguish between clinically meaningful and harmless textual variations, collapsing report quality into a single scalar score. Although Large Language Models (LLMs) embody richer medical knowledge, such metrics still lack an explicit boundary of clinical significance. To bridge this gap, we adopt the ReEvalMed benchmark as testbed and evaluate metric-level clinical significance from detecting true clinical errors ("Discrimination") and tolerating insignificant variations ("Robustness"). We design an evaluation framework with one-pass and two-pass settings, and compare 8 LLM evaluators against score-based baselines. Results reveal a discrimination bias: LLMs readily detect true clinical errors but struggle to tolerate harmless variations. To mitigate this, we synthesize 4k report pairs and train lightweight interpretable metrics on Qwen3-8B and MedGemma-4B. Our trained metric sharpens the clinical significance boundary, surpassing 32B-scale medical LLMs and remaining competitive with proprietary models. Notably, two-pass inference does not eliminate errors, but redistributes them between discrimination and robustness. We will release the dataset and metric to advance future research.
Anthology ID:
2026.findings-emnlp.1788
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
38237–38264
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1788/
DOI:
Bibkey:
Cite (ACL):
Qingyu Lu, Ruochen Li, Liang Ding, Yufei Xia, Youxiang Zhu, and Dacheng Tao. 2026. Beyond Scalar Scores: Exploring LLM-based Metrics for Clinical Significance Evaluation in Radiology Reports. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 38237–38264, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Beyond Scalar Scores: Exploring LLM-based Metrics for Clinical Significance Evaluation in Radiology Reports (Lu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1788.pdf