mistral-medqa-lora-v3

Mistral-7B MedQA QLoRA Adapter

This is a QLoRA adapter for mistralai/Mistral-7B-v0.3, fine-tuned on the MedQA-USMLE 4-option multiple-choice dataset.

It is part of a larger project on reliability-aware medical QA, selective prediction, and learned abstention.

GitHub project:

https://github.com/Tharun2908/mistral-medqa-abstention

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Intended Use

This adapter is intended for:

• research on medical QA reliability
• selective prediction and abstention experiments
• evaluation of confidence-based and learned abstention methods
• educational and portfolio demonstration

It is not intended for clinical decision-making.

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Out-of-Scope Use

Do not use this model for:

• real patient diagnosis
• treatment recommendations
• clinical triage
• emergency medical decisions
• replacing medical professionals

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Training Data

Dataset:

GBaker/MedQA-USMLE-4-options

Task format:

• Medical question
• Four answer options: A, B, C, D
• Model predicts the correct option

The dataset contains USMLE-style multiple-choice questions and does not represent open-ended clinical consultation.

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Method

Base model:

mistralai/Mistral-7B-v0.3

Fine-tuning method:

• QLoRA
• 4-bit quantization
• LoRA rank: 16
• LoRA alpha: 32
• Target modules: q_proj, v_proj

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Evaluation Summary

On the MedQA-USMLE test split:

The SFT adapter was also used as the starting point for post-hoc confidence thresholding and later warm-start + DPO learned-abstention experiments.

Note: this Hugging Face repository contains the SFT QLoRA adapter. DPO learned-abstention checkpoints are reported in the GitHub repository results, but are not hosted here.

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Selective Prediction Context

The larger project studies two abstention approaches:

1. Post-hoc confidence thresholding using A/B/C/D answer probabilities.
2. Learned abstention using warm-start SFT + DPO, where the model learns an explicit abstention completion:

I cannot answer confidently.

Final learned-abstention checkpoints reduced dataset-level wrong answers from about 48% to 7-17%, depending on the selected coverage/safety operating point.

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Limitations

• Evaluated only on multiple-choice USMLE-style questions.
• Not evaluated for open-ended clinical advice.
• Not clinically validated.
• May produce incorrect medical answers.
• Should not be used for real medical decisions.
• Performance depends on prompt format and evaluation method.

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Ethical and Safety Notes

Medical QA models can produce plausible but incorrect answers. This adapter is provided for research and educational purposes only.

Any clinical use would require:

• domain expert validation
• extensive safety testing
• calibration on held-out data
• uncertainty estimation
• regulatory and institutional review

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Citation / Attribution

If using this adapter or project, please cite or link the GitHub repository:

https://github.com/Tharun2908/mistral-medqa-abstention