Guideline Concordance of Large Language Model Responses to Parent-oriented Guideline Prompts About Pediatric Acute Bacterial Arthritis

BACKGROUND: Large language models (LLMs) are increasingly used by patients and caregivers to obtain medical information. In pediatric acute bacterial arthritis, non-guideline-concordant information may be clinically important because timely diagnosis and management are essential. This study evaluated the concordance of LLM-generated responses to parent-oriented reformulations of Pediatric Infectious Diseases Society/Infectious Diseases Society of America (PIDS/IDSA) guideline recommendations. METHODS: In this exploratory cross-sectional benchmarking study, 27 PIDS/IDSA guideline-derived recommendations and good practice statements were reformulated into standardized parent-oriented prompts. The same prompts were submitted to GPT-5.4 Thinking, Gemini 3 Thinking and Claude 4.6 Sonnet through browser-based interfaces on April 12, 2026. Responses were anonymized and independently assessed by 3 blinded reviewers. Each response was classified as concordant or discordant; final classifications were determined by majority decision. Interrater agreement was assessed using Fleiss' kappa, and model differences were evaluated using Cochran's Q test. RESULTS: Overall, 75 of 81 responses (92.6%) were concordant with PIDS/IDSA recommendations. Gemini 3 Thinking achieved concordance in 27/27 responses (100.0%), Claude 4.6 Sonnet in 25/27 (92.6%) and GPT-5.4 Thinking in 23/27 (85.2%). Cochran's Q test showed no significant difference among models (Q = 4.800, df = 2, P = 0.091). No unsupported or hallucinated content was identified. Interrater agreement was moderate (κ = 0.580; 95% CI, 0.454-0.706; P < 0.001). CONCLUSIONS: LLMs showed high guideline concordance, but selected item-level discordance persisted. Because these models may have been trained on guideline-derived content, high concordance should not be equated with independent clinical reasoning. These tools may support caregiver-oriented education but should not replace clinician assessment or guideline-based care.