VeriSim: A Configurable Framework for Stress-Testing Medical AI Under Patient Communication Noise

Sina Mansouri, Mohit Marvania, Vibhavari Shihorkar, Han Ngoc Tran, Kazhal Shafiei, Mehrdad Fazli, Yikuan Li, Ziwei Zhu


Abstract
Medical large language models are typically evaluated on idealized patient cases that do not reflect how real patients communicate. We introduce VeriSim, a patient simulation framework that injects controllable noise along six clinically grounded communication dimensions while substantially preserving each patient’s medical record. Truth adherence is supported by a verifier that extracts atomic claims from each candidate utterance and judges them against a UMLS-grounded vector index built with BioLORD embeddings, using the retrieved atoms’ structured clinical metadata (e.g., drug class, anatomical site, treats-condition relations) rather than surface-text similarity alone. Across seven open-weight LLMs, realistic noise reduces diagnostic accuracy by 15-25 percentage points and increases conversation length by 34-55%; the 7-8B models degrade 1.4x more than 70B+ models. A board-certified physician and a licensed nurse rate VeriSim’s conversations highly on truth, realism, clinical utility, and noise fidelity (inter-annotator agreement >=0.80 across all dimensions), and an LLM-as-judge closely tracks their ratings, enabling scalable evaluation.
Anthology ID:
2026.findings-emnlp.2109
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
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Pages:
44933–44958
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URL:
https://aclanthology.org/2026.findings-emnlp.2109/
DOI:
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Cite (ACL):
Sina Mansouri, Mohit Marvania, Vibhavari Shihorkar, Han Ngoc Tran, Kazhal Shafiei, Mehrdad Fazli, Yikuan Li, and Ziwei Zhu. 2026. VeriSim: A Configurable Framework for Stress-Testing Medical AI Under Patient Communication Noise. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 44933–44958, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
VeriSim: A Configurable Framework for Stress-Testing Medical AI Under Patient Communication Noise (Mansouri et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2109.pdf