Introduction:
Artificial intelligence (AI)-based large language models (LLMs) are promising tools for clinical decision support, but their clinical performance in specialized fields such as nephrology is still uncertain. ChatGPT and Claude represent distinct AI architectures with potentially different clinical utilities. We aimed to compare the diagnostic accuracy, treatment recommendations, and overall clinical utility of these two AI models in managing real-life difficult nephrology cases.

Material and methods:
Twenty-two real nephrology cases from a tertiary care university hospital were presented to both models, covering disorders such as glomerulonephritis, acute kidney injury, vasculitis, and transplant complications. Each model’s output was assessed for diagnostic accuracy, risk evaluation, test recommendations, and treatment planning. Three independent nephrologists evaluated the responses using the Quality Assessment of Medical Information (QAMAI) and Global Quality Score (GQS) tools. Statistical comparisons were performed using the Wilcoxon signed-rank test, with p < 0.05 considered significant.

Results:
Claude achieved higher diagnostic accuracy than ChatGPT (4.59 ±0.41 vs. 4.36 ±0.48; p = 0.048), whereas ChatGPT scored better in clarity (4.63 ±0.30 vs. 4.32 ±0.29; p = 0.002). No significant differences were found in relevance, completeness, usefulness, or source citation. Overall QAMAI scores were comparable between the two models (ChatGPT: 23.72 ±1.46; Claude: 23.39 ±1.43; p = 0.371). Inter-rater reliability ranged from moderate to good, with the highest agreement observed for ChatGPT’s GQS.

Conclusions:
Both ChatGPT and Claude demonstrate notable potential as decision-support tools in nephrology. Claude provided slightly higher diagnostic accuracy, while ChatGPT offered greater clarity. Despite these promising results, clinical judgment remains essential when interpreting LLM-generated suggestions.