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Mourad Oussalah

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Conference Open access Aug 2026

Causal Evidence Extraction and Triangulation in Crisis Reports using Large Language Models: A ReliefWeb-based Study

Humanitarian reports are long, noisy, and multi-topic, making it difficult to consolidate decision-relevant causal evidence. We present a ReliefWeb study (2000-2024) and a two-stage Large Language Model (LLM) pipeline that extracts structured intervention-outcome records with direction and strength attributes. Query-conditioned extraction restricts output to a specified intervention class, reducing retrieval-induced over-extraction, while snippet grounding links each relation to supporting text for auditability and classification. In an expert-annotated dataset of 100 reports, the best closed-source LLM achieved a weighted F1 score of 90.73% with strong cost-efficiency, while Llama-3.1-8B with supervised fine-tuning reached 94.15% weighted F1 score. We further propose context-preserving triangulation that aggregates strength-weighted evidence within disaster$\times$source cells, applies Laplace smoothing and equally weights cells to quantify cross-context convergence via a Level-of-Evidence score. Applied to cash assistance, food-related outcomes show strong positive convergence (LoE=0.865) and stable long-horizon trajectories.

Yuanjun Zhang, Mourad Oussalah · 0 citations
Open access 2026

Beyond Lexical Similarity: Evaluating Faithfulness in LLM-Based Medical Question Reformulation

Medical query rewriting transforms verbose consumer health questions into concise clinical queries, a critical step in health information retrieval. Large language models (LLMs) perform well on this task by standard metrics, yet high ROUGE or BERTScore does not guarantee preservation of clinical content. To address this issue, we introduce MedFaith-F1 , a category-level faithfulness metric over four clinically salient categories: clinical problems, medications, procedures, and follow-up intent. We further propose a hybrid Evidence and Knowledge-Grounded Retrieval-Augmented Generation ( EKG-RAG ), an evidence and knowledge-grounded framework combining hybrid retrieval over PubMed and MedlinePlus resources with UMLS (Unified Medical Language System)-aligned ontology grounding. Evaluating LLMs LLaMA-3 and Qwen2.5 across zero-shot, few-shot, and QLoRA settings on MeQSum and medical question-pair (MQP) datasets revealed that base models exhibit category-level faith-fulness failure rates (CHR) exceeding 40%, invisible to standard metrics, while EKG-RAG with QLoRA reduces CHR to 26.75%, achieving MedFaith-F1 of 0.73. Our findings call for faithfulness-aware evaluation in clinical query rewriting, and MedFaith-F1 provides a reproducible step in that direction.

Md Rabiul Hasan, Aleka Melese Ayalew, Mourad Oussalah · 0 citations