MedAction: Towards Active Multi-turn Clinical Diagnostic LLMs

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Hauptverfasser: Hsu, Hsin-Ling, Wang, Zizheng, Zhang, Donghua, Chen, Nai-Chia, Wang, Jerry, Ding, Jun-En, Hsu, Chia-Hsuan, Wang, Guoan, Liu, Feng, Hung, Fang-Ming, Wu, Chenwei, Shen, Liyue
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Veröffentlicht: 2026
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author Hsu, Hsin-Ling
Wang, Zizheng
Zhang, Donghua
Chen, Nai-Chia
Wang, Jerry
Ding, Jun-En
Hsu, Chia-Hsuan
Wang, Guoan
Liu, Feng
Hung, Fang-Ming
Wu, Chenwei
Shen, Liyue
author_facet Hsu, Hsin-Ling
Wang, Zizheng
Zhang, Donghua
Chen, Nai-Chia
Wang, Jerry
Ding, Jun-En
Hsu, Chia-Hsuan
Wang, Guoan
Liu, Feng
Hung, Fang-Ming
Wu, Chenwei
Shen, Liyue
contents Most existing LLM diagnoses are evaluated on static, single-turn settings where complete patient information is provided upfront, an oversimplification of real clinical practice. We study active diagnosis: the real-life clinical process of starting from initial observation, ordering tests, interpreting results, and updating a differential diagnosis across multiple turns. Through systematic analysis, we identify three recurring failure modes in current LLMs: ungrounded test ordering, unreliable diagnostic update, and degraded multi-turn coherence. Together, these failures reveal a core deficit: existing medical training data teaches models to reason from complete information but not to act under evolving, partial evidence. To address this gap, we introduce MedAction, a tree-structured distillation pipeline that synthesizes diverse and high-quality multi-turn diagnostic trajectories via LLM-environment interaction. We propose two knowledge-graph-grounded metrics to filter trajectory quality: Disease Trajectory Consistency (DTC), which tracks whether the model's hypothesis converges toward the correct diagnosis, and Reasoning-Action Consistency (RAC), which verifies that belief updates are driven by gathered evidence. Using this pipeline, we construct MedAction-32K, a dataset of 32,681 trajectories from 2,896 PMC cases. Fine-tuning an 8B model on MedAction-32K achieves state-of-the-art performance among open-source models on both MedR-Bench and our curated MedAction-300-Hard benchmark, pushing the edge for open-source medical LLMs.
format Preprint
id arxiv_https___arxiv_org_abs_2605_07305
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle MedAction: Towards Active Multi-turn Clinical Diagnostic LLMs
Hsu, Hsin-Ling
Wang, Zizheng
Zhang, Donghua
Chen, Nai-Chia
Wang, Jerry
Ding, Jun-En
Hsu, Chia-Hsuan
Wang, Guoan
Liu, Feng
Hung, Fang-Ming
Wu, Chenwei
Shen, Liyue
Computation and Language
Artificial Intelligence
Most existing LLM diagnoses are evaluated on static, single-turn settings where complete patient information is provided upfront, an oversimplification of real clinical practice. We study active diagnosis: the real-life clinical process of starting from initial observation, ordering tests, interpreting results, and updating a differential diagnosis across multiple turns. Through systematic analysis, we identify three recurring failure modes in current LLMs: ungrounded test ordering, unreliable diagnostic update, and degraded multi-turn coherence. Together, these failures reveal a core deficit: existing medical training data teaches models to reason from complete information but not to act under evolving, partial evidence. To address this gap, we introduce MedAction, a tree-structured distillation pipeline that synthesizes diverse and high-quality multi-turn diagnostic trajectories via LLM-environment interaction. We propose two knowledge-graph-grounded metrics to filter trajectory quality: Disease Trajectory Consistency (DTC), which tracks whether the model's hypothesis converges toward the correct diagnosis, and Reasoning-Action Consistency (RAC), which verifies that belief updates are driven by gathered evidence. Using this pipeline, we construct MedAction-32K, a dataset of 32,681 trajectories from 2,896 PMC cases. Fine-tuning an 8B model on MedAction-32K achieves state-of-the-art performance among open-source models on both MedR-Bench and our curated MedAction-300-Hard benchmark, pushing the edge for open-source medical LLMs.
title MedAction: Towards Active Multi-turn Clinical Diagnostic LLMs
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2605.07305