MedScope: A Lightweight Benchmark of Open-Source Large Language Models for Medical Question Answering

The rapid development of large language models (LLMs) has stimulated growing interest in their use for medical question answering and clinical decision support. However, compared with frontier proprietary systems, the empirical understanding of lightweight open-source LLMs in medical settings remains limited, particularly under resource-constrained experimental conditions. To address this gap, we introduce MedScope, a lightweight benchmarking framework for systematically evaluating open-source LLMs on medical multiple-choice question answering. Using 1,000 sampled questions from MedMCQA, we benchmark six lightweight open-source models spanning three representative model families: LLaMA, Qwen, and Gemma. Beyond standard predictive metrics such as accuracy and macro-F1, our framework additionally considers inference time, prediction consistency, subject-wise variability, and model-specific error patterns. We further develop a set of multi-perspective visual analyses, including clustered heatmaps, agreement matrices, Pareto-style trade-off plots, radar charts, and multi-panel summary figures, in order to characterize model behavior in a more interpretable and comprehensive manner. Our results reveal substantial heterogeneity across models in predictive performance, efficiency, and subject-level robustness. While larger lightweight models generally achieve better overall results, the gain is neither uniform across subject categories nor always aligned with efficiency. These findings suggest that lightweight open-source LLMs remain valuable as transparent and reproducible medical AI baselines, but their current capabilities are still insufficient for unsupervised deployment in high-risk healthcare scenarios. MedScope provides an accessible benchmark for evaluating lightweight medical LLMs and emphasizes the need for multi-dimensional assessment beyond accuracy alone.The relevant code is now open-sourced at: https://github.com/VhoCheng/MedScope.