Cited by 352Artificial Intelligence in Healthcare and EducationTopic ModelingMultimodal Machine Learning Applications

The DOI matches its Crossref record; 81 of the 81 references it cites were found in a registry or an index; none of the 19 sources its claims cite is checked for support yet.

Can large language models reason about medical questions?

Open access

Abstract

Although large language models often produce impressive outputs, it remains unclear how they perform in real-world scenarios requiring strong reasoning skills and expert domain knowledge. We set out to investigate whether closed- and open-source models (GPT-3.5, Llama 2, etc.) can be applied to answer and reason about difficult real-world-based questions. We focus on three popular medical benchmarks (MedQA-US Medical Licensing Examination [USMLE], MedMCQA, and PubMedQA) and multiple prompting scenarios: chain of thought (CoT; think step by step), few shot, and retrieval augmentation. Based on an expert annotation of the generated CoTs, we found that InstructGPT can often read, reason, and recall expert knowledge. Last, by leveraging advances in prompt engineering (few-shot and ensemble methods), we demonstrated that GPT-3.5 not only yields calibrated predictive distributions but also reaches the passing score on three datasets: MedQA-USMLE (60.2%), MedMCQA (62.7%), and PubMedQA (78.2%). Open-source models are closing the gap: Llama 2 70B also passed the MedQA-USMLE with 62.5% accuracy.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This paper evaluates whether GPT-3.5 and open-source LLMs can answer and reason about medical questions across MedQA-USMLE, MedMCQA, and PubMedQA using prompting, chain-of-thought (CoT), retrieval augmentation, and ensembling. It finds that LLMs can often reason and recall expert knowledge, and that Codex 5-shot CoT with many samples reaches passing scores on all three benchmarks.

Key findings

  • Zero-shot InstructGPT outperformed the best fine-tuned BERT baselines on all three datasets: +1.4% on USMLE, +1.0% on MedMCQA, and +1.1% on PubMedQA.
  • Expert annotation of 50 USMLE CoTs found that incorrect answers often contained reasoning errors (86%), insufficient/incorrect knowledge (74%), and reading-comprehension failures (50%); still, 59% of CoTs leading to incorrect answers contained at least one correct reasoning step and 65% showed correct knowledge recall.
  • Codex 5-shot CoT with an ensemble of up to k=100 samples reached passing scores: USMLE 60.2%, MedMCQA 62.7%, and PubMedQA 78.2%; Llama 2 70B also passed USMLE with 62.5% accuracy.
  • Codex 5-shot CoT and Llama 2 were close to well calibrated, though calibration was worse for PubMedQA; prompting also induced answer-position biases, with direct prompting overestimating C/D and underestimating A, and CoT prompting underestimating B/C while overestimating D.

Methods

  • The study used three medical multiple-choice QA datasets: MedQA-USMLE, MedMCQA, and PubMedQA, with questions and reference explanations used for few-shot CoT prompts.
  • Models included closed-source GPT-3.5 series (InstructGPT, text-davinci-002; Codex, code-davinci-002) and open-source models from 7B to 70B parameters, including Llama 2, Vicuna, Guanaco, Falcon, MPT, and GPT-NeoX.
  • Prompting conditions included zero-shot direct, zero-shot CoT with domain-specific cues, few-shot direct/CoT, BM25 retrieval augmentation over Wikipedia, and ensemble/self-consistency sampling up to k=100 completions; a medical expert annotated 50 generated CoTs using six success/failure patterns.

Limitations

  • The paper states that deploying LLMs in clinical scenarios requires more robust techniques, that it exposed only one form of bias (answer-option ordering), and that many more biases may exist, including hidden training-data biases such as gender and race.
  • The paper notes that benchmark contamination in training sets is a valid concern for both proprietary and open-source LLMs, and that a large gap remains between the models and human experts despite passing scores.
  • Evident from the text: the expert CoT evaluation is based on a subset of only 50 USMLE CoTs annotated by one medical expert, and the BM25 retrieval experiment is described as limited.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1016/j.patter.2024.100943

Cites

81 of 81 references verified0 citation errors · 0 not checkable

Statistics

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Figures

Graphical abstract
Graphical abstract CC BY · PubMed Central
Figure 1 Answering a USMLE (US Medical Licensing Examination) question using zero-shot CoT prompting “Let’s think step by step” and InstructGPT Selected example.
Figure 1 Answering a USMLE (US Medical Licensing Examination) question using zero-shot CoT prompting “Let’s think step by step” and InstructGPT Selected example.CC BY · PubMed Central
Figure 2 Prompt templates In the table, we use typewriter style and brackets to represent [provided data] such as the question, additional context, or the answer and <completions> generated by GPT-3. The symbol ∅ represents an empty string.
Figure 2 Prompt templates In the table, we use typewriter style and brackets to represent [provided data] such as the question, additional context, or the answer and <completions> generated by GPT-3. The symbol ∅ represents an empty string.CC BY · PubMed Central
Figure 3 Generative process and answer likelihood (ensemble model, i.e., self-consistency)
Figure 3 Generative process and answer likelihood (ensemble model, i.e., self-consistency)CC BY · PubMed Central
Figure 4 Frequencies of USMLE answers and InstructGPT (text-davinci-002) predictions for direct and CoT prompts (no grounding, zero-shot)
Figure 4 Frequencies of USMLE answers and InstructGPT (text-davinci-002) predictions for direct and CoT prompts (no grounding, zero-shot)CC BY · PubMed Central
Figure 5 Sampling and combining multiple CoTs Answering accuracy of Codex 5-shot CoT (code-davinci-002) on the USMLE (test), the MedMCQA (validatuin), and the PubMedQA (test) datasets for 100 CoTs sampled with temperature τ∈{0,0.5}. We report the average accuracy for ensemble models evaluated using random subsets of k^(′)=1…100 CoTs. We report the mean and standard deviation. We display the performances of the best fine-tuned methods along with the lower human baselines.
Figure 5 Sampling and combining multiple CoTs Answering accuracy of Codex 5-shot CoT (code-davinci-002) on the USMLE (test), the MedMCQA (validatuin), and the PubMedQA (test) datasets for 100 CoTs sampled with temperature τ∈{0,0.5}. We report the average accuracy for ensemble models evaluated using random subsets of k^(′)=1…100 CoTs. We report the mean and standard deviation. We display the performances of the best fine-tuned methods along with the lower human baselines.CC BY · PubMed Central
Figure 6 Uncertainty quantification First row: distribution of the probability assigned to the correct label for correct predictions and incorrect predictions (see Equation 1). Second row: calibration plot. The probabilities are obtained using Codex 5-shot CoT and an ensemble of k=100 predictions sampled with temperature τ=0.5.
Figure 6 Uncertainty quantification First row: distribution of the probability assigned to the correct label for correct predictions and incorrect predictions (see Equation 1). Second row: calibration plot. The probabilities are obtained using Codex 5-shot CoT and an ensemble of k=100 predictions sampled with temperature τ=0.5.CC BY · PubMed Central
Figure 7 Comparing open-source LLMs against the closed-source Codex on the MedQA-USMLE benchmark (τ=0.9, up to k=100 samples) We report answering accuracy, model calibration, and answering bias.
Figure 7 Comparing open-source LLMs against the closed-source Codex on the MedQA-USMLE benchmark (τ=0.9, up to k=100 samples) We report answering accuracy, model calibration, and answering bias.CC BY · PubMed Central
Figure 8 MedQA-USMLE accuracy vs. model size All experiments were performed using a 5-shot CoT prompting strategy and greedy decoding (τ=0). Llama 2 70B outperforms Codex 175B (proprietary).
Figure 8 MedQA-USMLE accuracy vs. model size All experiments were performed using a 5-shot CoT prompting strategy and greedy decoding (τ=0). Llama 2 70B outperforms Codex 175B (proprietary).CC BY · PubMed Central
Figure 9 (Sample 1) Generated zero-shot CoT from InstructGPT text-davinci-002 for three CoT prompts on a sample for the MedQA-USMLE test set
Figure 9 (Sample 1) Generated zero-shot CoT from InstructGPT text-davinci-002 for three CoT prompts on a sample for the MedQA-USMLE test setCC BY · PubMed Central

Verification

Claims the paper makes

55 Own result · 11 Not checked yet · 10 Own interpretation · 5 No basis given · 2 Own method

Verify all 19 references — free account

Show all 56 claims

  • It may state two separate claims as one. 20
  • The quote only partly states this claim. 2
  • Probably not a substantial claim. 10
27 of 27
  • The paper relies on this without support.

    It was unclear how large language models perform in real-world scenarios requiring strong reasoning skills and expert domain knowledge.

    “Although large language models often produce impressive outputs, it remains unclear how they perform in real-world scenarios requiring strong reasoning skills and expert domain knowledge.”
  • The paper relies on this without support.

    At the time of the research, studies applying large language models to the medical domain were still needed.

    “At the dawn of this research work, although LLMs had been tested on large benchmarks (MMLU,31 BIG-bench18), studies applied to the medical domain were still needed.”
  • The paper relies on this without support.

    Large language models memorize part of the knowledge embedded into the training data.

    “LLMs memorize part of the knowledge embedded into the training data; nonetheless, models might fail to reuse this knowledge effectively during prediction.”
  • The paper relies on this without support.

    A single medical expert’s annotation is sufficient to evaluate the quality of generated CoTs.

    “A subset of 50 CoTs generated based on USMLE questions were annotated by a medical expert (C.E.H.) using the six categories.”
  • The paper relies on this without support.

    The generated CoTs reflect the model’s reasoning process.

    “The CoTs that result from that prompt not only appear to expose valid reasoning but also translate into superior zero-shot performances (see example in Figure 1).”
  • The paper relies on this without support.

    The USMLE, MedMCQA, and PubMedQA datasets are valid benchmarks for medical reasoning ability.

    “Zero-shot InstructGPT and Codex outperformed fine-tuned BERT models on three challenging question-answering datasets (see zero-shot benchmark and supplemental information section A).”
  • The paper relies on this without support.

    The chosen passing-score thresholds (60% for USMLE, 50% for MedMCQA, 78% for PubMedQA) are appropriate for defining passing.

    “Using an ensemble of the k samples, Codex 5-shot CoT reaches the passing score on the three tasks (see Table 1): the USMLE dataset (60.2% ≥ 60%), the MedMCQA dataset (62.7% ≥ 50%), and the PubMedQA dataset (78.2% ≥ 78%).”
  • The paper relies on this without support.

    The human baseline performances reported are valid lower bounds for human performance.

    “We report the best fine-tuned models and the human baseline.”
  • The paper relies on this without support.

    The expert evaluation of CoTs is a valid measure of soundness and interpretability.

    “Our expert evaluation (see expert evaluation of the generated CoTs) revealed that CoTs are often sound: even though InstructGPT still does make mistakes, it was often able to reason, recall medical knowledge, and comprehend the given problem.”
9 of 9

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Citations

Cites

  • Attention Is All You Need

    Vaswani, A., Shazeer, N., Parmar, N., Uszkoreit, J., Jones, L., Gomez, A. N., Kaiser, L., & Polosukhin, I. (2017) · arXiv · doi:10.48550/arxiv.1706.03762 · Cited by 120,404 · cited 2×

    “, 2018), language models are now ubiquitous in natural language processing, notably, thanks to the Transformer architecture (Vaswani et al., 2017) and its high compatibility with massively parallel computation hardware.”
    Background
  • MizAR 60 for Mizar 50

    Jakubův, J., Chvalovský, K., Goertzel, Z., et al. (2023) · DROPS (Schloss Dagstuhl – Leibniz Center for Informatics) · doi:10.4230/lipics.itp.2023.19 · Cited by 76,648

  • BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding

    Devlin, J., Chang, M.-W., Lee, K., & Toutanova, K. (2018) · arXiv · doi:10.48550/arxiv.1810.04805 · Cited by 73,173 · cited 1×

    “…word vectors (Mikolov et al., 2013; Pennington et al., 2014) to deep contextualized representations (Peters et al., 2018; Vaswani et al., 2017; Devlin et al., 2018; Radford et al., 2018), language models are now ubiquitous in natural language processing, notably, thanks to the Transformer…”
    Background
  • BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding

    Devlin, J., Chang, M.-W., Lee, K., & Toutanova, K. (2019) · Proceedings of the 2019 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, Volume 1 (Long and Short Papers) · doi:10.18653/v1/n19-1423 · Cited by 54,325 · cited 1×

    “…word vectors (Mikolov et al., 2013; Pennington et al., 2014) to deep contextualized representations (Peters et al., 2018; Vaswani et al., 2017; Devlin et al., 2018; Radford et al., 2018), language models are now ubiquitous in natural language processing, notably, thanks to the Transformer…”
    Background
  • Glove: Global Vectors for Word Representation

    Pennington, J., Socher, R., & Manning, C. (2014) · Proceedings of the 2014 Conference on Empirical Methods in Natural Language Processing (EMNLP) · doi:10.3115/v1/d14-1162 · Cited by 34,071 · cited 1×

    “Language representations have transformed the field of natural language processing, from simple word vectors (Mikolov et al., 2013; Pennington et al., 2014) to deep contextualized representations (Peters et al.”
    Background
  • Distributed Representations of Words and Phrases and their Compositionality

    Mikolov, T., Sutskever, I., Chen, K., Corrado, G., & Dean, J. (2013) · arXiv · doi:10.48550/arxiv.1310.4546 · Cited by 24,533 · cited 1×

    “Language representations have transformed the field of natural language processing, from simple word vectors (Mikolov et al., 2013; Pennington et al., 2014) to deep contextualized representations (Peters et al., 2018; Vaswani et al., 2017; Devlin et al., 2018; Radford et al., 2018), language models…”
    Background
  • Language Models are Few-Shot Learners

    Brown, T. B., Mann, B., Ryder, N., Subbiah, M., Kaplan, J., Dhariwal, P., Neelakantan, A., Shyam, P., Sastry, G., Askell, A., et al. (2020) · arXiv · doi:10.48550/arxiv.2005.14165 · Cited by 23,372

  • Deep Contextualized Word Representations

    Peters, M., Neumann, M., Iyyer, M., Gardner, M., Clark, C., Lee, K., & Zettlemoyer, L. (2018) · Proceedings of the 2018 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, Volume 1 (Long Papers) · doi:10.18653/v1/n18-1202 · Cited by 11,983

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    Kaplan, J., McCandlish, S., Henighan, T., Brown, T. B., Chess, B., Child, R., Gray, S., Radford, A., Wu, J., & Amodei, D. (2020) · arXiv · doi:10.48550/arxiv.2001.08361 · Cited by 9,550 · cited 1×

    “This so far translated sustain gains (Kaplan et al., 2020), enabled new ways to interact with language models and made many of the past benchmarks obsolete; which triggered a community-wide effort to design a sufficiently difficult benchmarks (e.”
    Background
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Research works printed but not linked: 1

  1. Lieber, 2021, Jurassic-1: Technical details and evaluation, White Paper AI21 Labs, 1, 9

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Metadata

Authors
Liévin, V., Hother, C. E., Motzfeldt, A. G., & Winther, O.
Affiliations
  • Technical University of Denmark (DK)
  • Copenhagen University Hospital (DK)
  • University of Copenhagen (DK)
Corresponding author
Liévin, Valentin
Venue
Patterns
Publisher
Elsevier BV
Published
2024-03
Volume
5
Issue
3
Pages
100943
ISSN
2666-3899 (ISSN-L)
OpenAlex
W4392359953
Cited by
343
References
69
Citations by year
2026: 95 · 2025: 108 · 2024: 79
FWCI
26.42
Type
journal article
Language
en
Open access
Locations
  • Patterns (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Research at the University of Copenhagen (University of Copenhagen) (publishedVersion, cc-by)
  • arXiv (Cornell University) (submittedVersion)
  • Technical University of Denmark, DTU Orbit (Technical University of Denmark, DTU) (submittedVersion, cc-by)
  • arXiv (Cornell University)
Funders
  • Danmarks Grundforskningsfond
  • Novo Nordisk Fonden (NNF20OC0062606)
Topics
  • Health Sciences › Medicine › Health Informatics › Artificial Intelligence in Healthcare and Education
  • Physical Sciences › Computer Science › Artificial Intelligence › Topic Modeling
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Multimodal Machine Learning Applications
Keywords
large language models, medical question answering, medical reasoning, chain-of-thought prompting, retrieval augmentation, few-shot prompting, prompt engineering, open-source language models, Llama 2, GPT-3.5, MedMCQA, PubMedQA

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