Dax M. Westerman

dblp:200/4466 · DBLP profile ↗
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8ranked-venue papers
1as first author
5since 2021 · last 2025
—ORCID · none

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Applied, interdisciplinary, general and emerging computing · 8 · 1 first-author · 5 since 2021
YearPublicationVenuePosition
2025 A machine learning framework to adjust for learning effects in medical device safety evaluation
abstract
OBJECTIVES: Traditional methods for medical device post-market surveillance often fail to accurately account for operator learning effects, leading to biased assessments of device safety. These methods struggle with non-linearity, complex learning curves, and time-varying covariates, such as physician experience. To address these limitations, we sought to develop a machine learning (ML) framework to detect and adjust for operator learning effects. MATERIALS AND METHODS: A gradient-boosted decision tree ML method was used to analyze synthetic datasets that replicate the complexity of clinical scenarios involving high-risk medical devices. We designed this process to detect learning effects using a risk-adjusted cumulative sum method, quantify the excess adverse event rate attributable to operator inexperience, and adjust for these alongside patient factors in evaluating device safety signals. To maintain integrity, we employed blinding between data generation and analysis teams. Synthetic data used underlying distributions and patient feature correlations based on clinical data from the Department of Veterans Affairs between 2005 and 2012. We generated 2494 synthetic datasets with widely varying characteristics including number of patient features, operators and institutions, and the operator learning form. Each dataset contained a hypothetical study device, Device B, and a reference device, Device A. We evaluated accuracy in identifying learning effects and identifying and estimating the strength of the device safety signal. Our approach also evaluated different clinically relevant thresholds for safety signal detection. RESULTS: Our framework accurately identified the presence or absence of learning effects in 93.6% of datasets and correctly determined device safety signals in 93.4% of cases. The estimated device odds ratios' 95% confidence intervals were accurately aligned with the specified ratios in 94.7% of datasets. In contrast, a comparative model excluding operator learning effects significantly underperformed in detecting device signals and in accuracy. Notably, our framework achieved 100% specificity for clinically relevant safety signal thresholds, although sensitivity varied with the threshold applied. DISCUSSION: A machine learning framework, tailored for the complexities of post-market device evaluation, may provide superior performance compared to standard parametric techniques when operator learning is present. CONCLUSION: Demonstrating the capacity of ML to overcome complex evaluative challenges, our framework addresses the limitations of traditional statistical methods in current post-market surveillance processes. By offering a reliable means to detect and adjust for learning effects, it may significantly improve medical device safety evaluation.
Jejo Koola, Karthik Ramesh, Jialin Mao, Minyoung Ahn, Sharon E. Davis, Usha Govindarajulu, Amy Perkins, Dax M. Westerman, Henry Ssemaganda, Theodore Speroff, Lucila Ohno-Machado, Craig Ramsay, Art Sedrakyan, Frederic S. Resnic, Michael E. Matheny
J. Am. Medical Informatics Assoc.8
2022 A Framework for Generating Synthetic Clinical Datasets with Learning Effects to Support Methods Development and Validation
Sharon E. Davis, Henry Ssemaganda, Jejo Koola, Jialin Mao, Dax M. Westerman, Theodore Speroff, Usha Govindarajulu, Craig Ramsay, Lucila Ohno-Machado, Frederic S. Resnic, Michael E. Matheny
AMIA5
2022 A Framework for Detecting Medical Device Safety Signals Confounded by Learning Effects Using Machine Learning
Jejo Koola, Jialin Mao, Sharon E. Davis, Henry Ssemaganda, Dax M. Westerman, Lucila Ohno-Machado, Frederic S. Resnic, Michael E. Matheny
AMIA5
2022 Disentangling and Characterizing Device Safety Signals and Learning Effects
Henry Ssemaganda, Frederic S. Resnic, Sharon E. Davis, Usha Govindarajulu, Jejo Koola, Jialin Mao, Dax M. Westerman, Theodore Speroff, Craig Ramsay, Art Sedrakyan, Lucila Ohno-Machado, Michael E. Matheny
AMIA7
2022 AUTO-PILOT: Development and Validation of a Tool to Extract Structured Data in Interfacility Transfer Paperwork
Jesse O. Wrenn, Sara Lin, Ruth Reeves, Dax M. Westerman, Michael E. Matheny, Michael J. Ward
AMIA5
2018 Integrating Cancer Genomic Data into Decision Support at the VA: Hematologic Oncology as a Use Case
Dax M. Westerman, Fern FitzHenry, Michael E. Matheny, Michele L. LeNoue-Newton, Claudio A. Mosse, Ian Maurer, Matthew Stachowiak, Justin A. Yeakley, James Cole, Regina M. Thomas, Mia A. Levy
AMIA1
2016 Workflow-guided development of a clinical decision support tool for patients with advanced liver disease
Samuel B. Ho, Julie Ducom, Jennifer H. Garvin, Jejo Koola, Russ Beebe, Jason Slagle, Dax M. Westerman, Carrie Reale, Matthew B. Weinger, Erik Groessl, Michael E. Matheny
AMIA8
2016 An Integrated Privacy Preserving Collaborative Analytics Platform: The PCORnet pSCANNER-PopMedNet TM Software Suite
Michael E. Matheny, Dax M. Westerman, Laura Pearlman, Josh Gieringer, Xiaoqian Jiang, Claudiu Farcas, Tara K. Knight, Shuang Wang 0002, Amy Perkins, Lucila Ohno-Machado, Bill Clarke, Daniella Meeker
AMIA2