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Finite State Machine-Guided Retrieval-Augmented Generation Improves Expert-Rated Acceptability of a Peripherally Inserted Central Catheter Self-Management Chatbot: Single-Center Content Validation Study

Lee M, Cho SB, Yu JW, Yoon J, Choi JB, Jung KH, Cho J

Journal of medical Internet research, 2026

Abstract

Background: Patients with cancer undergoing long-term or vesicant chemotherapy frequently require peripherally inserted central catheters (PICCs). Due to the nature of ambulatory treatment administration, self-PICC management is essential for the continuation and completion of the planned treatment. Large language models offer potential for continuous patient support, but hallucinations and insufficient adherence to clinical protocols remain concerns. Fine-tuning (FT) and retrieval-augmented generation (RAG) improve factual grounding but cannot enforce the structured decision logic of expert-led PICC consultations, leaving the value of dialogue-control mechanisms unclear.

Objective: This study is an expert-panel evaluation designed to exploratorily verify whether a finite state machine (FSM)-guided RAG architecture yields incremental gains in clinical acceptability when added on top of FT and RAG compared with simpler architectures (fine-tuned model alone; fine-tuned model with RAG).

Methods: We conducted a blinded ablation comparison of three chatbot architectures sharing an identical fine-tuned GPT-4o-mini base: model 1 (fine-tuning only; FT), model 2 (FT + RAG), and model 3 (FT + RAG + FSM). Three nurses specializing in PICC management (≥10 y experience) independently evaluated responses to 43 PICC-related queries. The two-stage evaluation comprised query-level forced-choice preference and global Likert ratings across 8 predefined dimensions. Interrater agreement was…

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