Investigating LLM Capabilities on Long Context Comprehension for Clinical Question Answering

Feras AlMannaa, Talia Tseriotou, Jenny Chim, Maria Liakata


Abstract
Despite the impressive reported performance of Large Language Models (LLMs) on medical Question-Answering (QA), evaluation still overrelies on multiple-choice and extractive settings primarily assessing textbook knowledge, with limited work on open-ended QA over patient records. We present a comprehensive study investigating LLM long-context (LC) comprehension on longitudinal, patient-centric Electronic Health Records (EHRs) across multiple datasets, models and metrics, covering extractive, multiple-choice, and open-ended generative QA under different context formulation and Retrieval Augmented Generation (RAG) settings. We show that medically fine-tuned models offer no measurable benefit over base counterparts, smaller models exhibit stronger memorization, and longitudinal supplementary notes aid generative QA. Reasoning models gain on complex multi-note QA under LLM Correctness but not stricter reference-aligned metrics, while hybrid RAG with reranking outperforms Full-Context (FC) prompting. A question-category analysis and multi-faceted metric evaluation further reveal where RAG and FC excel and struggle, with RAG falling behind in longitudinal reasoning, thus uncovering systematic failures pointing to the need for reasoning-appropriate metrics.
Anthology ID:
2026.aacl-long.56
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1188–1213
Language:
URL:
https://aclanthology.org/2026.aacl-long.56/
DOI:
Bibkey:
Cite (ACL):
Feras AlMannaa, Talia Tseriotou, Jenny Chim, and Maria Liakata. 2026. Investigating LLM Capabilities on Long Context Comprehension for Clinical Question Answering. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 1188–1213, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Investigating LLM Capabilities on Long Context Comprehension for Clinical Question Answering (AlMannaa et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.56.pdf