MIMIC-CTRL-2026: A Realistic Clinical Trial Dataset to Benchmark LLM performance

Noshin Nawal, Robert Margaryan, Moustafa Abdalla, Justin A. Ezekowitz, Mohamed Abdalla


Abstract
Patient recruitment remains a major barrier in clinical trials, as identifying eligible participants often requires manual screening of complex health records, contributing significantly to trial delays and increased costs. While Large Language Models (LLMs) offer potential to automate this process, existing public datasets are overly simplistic in their patient representation: they pair full criterion lists with single-paragraph synthetic summaries, failing to capture the longitudinal complexity of real clinical records. We introduce MIMIC-CTRL-2026, a dataset of 800 manually labeled patient-criterion pairs grounded in real-world longitudinal EHR data from MIMIC-IV, annotated by clinically trained experts. Each instance pairs one eligibility criterion with a full patient record spanning multiple discharge notes, radiology reports, lab values, and medication histories. While simple prompting achieves high performance (κ = 0.84) on existing benchmarks, it collapses (κ = 0.06) on our dataset, revealing a substantial benchmark-difficulty gap between simplified and real-world clinical evaluation. Lastly, we present a framework combining structured pre-processing with a clinician-validated expanded prompt that substantially outperforms naive baselines without any model fine-tuning, establishing a realistic benchmark for automated clinical trial screening on real EHR data. Our dataset and code are available at: https://doi.org/10.5281/zenodo.22103011
Anthology ID:
2026.findings-emnlp.1297
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:
27428–27452
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1297/
DOI:
10.18653/2026.findings-emnlp.1297
Bibkey:
Cite (ACL):
Noshin Nawal, Robert Margaryan, Moustafa Abdalla, Justin A. Ezekowitz, and Mohamed Abdalla. 2026. MIMIC-CTRL-2026: A Realistic Clinical Trial Dataset to Benchmark LLM performance. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 27428–27452, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
MIMIC-CTRL-2026: A Realistic Clinical Trial Dataset to Benchmark LLM performance (Nawal et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1297.pdf