Large language models demonstrate variable diagnostic performance and a systematic risk of undertriage in surgical triage of feline metacarpal and metatarsal fractures.

OBJECTIVE: To evaluate the diagnostic performance of multiple large language models (LLMs) against expert consensus in determining surgical intervention needs for feline metacarpal and metatarsal fractures. METHODS: In this retrospective study (December 2023 to February 2025), 73 clinical cases of feline metacarpal and metatarsal fractures were evaluated. Two board-certified veterinary orthopedic surgeons established a reference standard for surgical versus conservative management. Five LLMs (ChatGPT, version 5.2 [OpenAI Inc]; Gemini, version 3 Pro [Alphabet Inc]; Grok, version 4.1 [SpaceXAI]; Qwen, version 3.5 [Alibaba Cloud]; and Claude Sonnet, version 4.5 [Anthropic PBC]; and Claude Sonnet, version 4.5 [Anthropic PBC]) assessed anonymized case summaries using a standardized zero-shot prompt. Model recommendations were compared with the reference standard to calculate accuracy, sensitivity, specificity, and the Cohen κ. RESULTS: The reference standard classified 49 cases (67.1%) as surgical and 24 (32.9%) as conservative. ChatGPT achieved the highest performance (accuracy, 84.9%; sensitivity, 79.6%; specificity, 95.8%; κ = 0.69). Other models showed lower performance; Qwen and Claude Sonnet failed to identify any surgical cases (0% sensitivity). A systematic bias toward conservative management was observed across all models, causing high false-negative rates (undertriage). CONCLUSIONS: LLMs demonstrate highly variable diagnostic performance and a systematic risk of undertriage in feline fracture assessment. While top-performing models approach expert-level agreement, others fail in critical clinical scenarios. CLINICAL RELEVANCE: Independent LLM use for surgical decision-making in feline orthopedics is not recommended due to undertriage risks. These tools require strict clinician oversight for preliminary triage.