Caveats for the Use of Operational Electronic Health Record Data in Comparative Effectiveness Research

Cited by (564)

Items 401–500 of 564

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    Tom M Toner, Rashi Pancholi, Paul Miller, Thorsten Forster, Helen G. Coleman, Ian M. Overton · 2022 · GigaScience
  2. Understanding enterprise data warehouses to support clinical and translational research: impact, sustainability, demand management, and accessibility
    Thomas R. Campion, Catherine K. Craven, David A Dorr, Elmer Victor Bernstam, Boyd M. Knosp · 2024 · Journal of the American Medical Informatics Association
  3. Data-Driven and Practice-Based Evidence
    Hamzah Osop, Tony R. Sahama · 2016 · IGI Global eBooks
  4. Healthcare Data Analytics
    William Hersh · 2014
  5. Accounting for Differential Error in Time-to-Event Analyses Using Imperfect Electronic Health Record-Derived Endpoints
    Rebecca A. Hubbard, Joanna G. Harton, Weiwei Zhu, Le Wang, Jessica Chubak · 2017 · ICSA book series in statistics
  6. Public Health Informatics in the Larger Context of Biomedical and Health Informatics
    William Hersh · 2020 · Health informatics
  7. How Confounder Strength Can Affect Allocation of Resources in Electronic Health Records.
    Kristine E. Lynch, Brian W. Whitcomb, Scott L. DuVall · 2018 · Europe PMC (PubMed Central)
  8. Using the Literature to Construct Causal Models for Pharmacovigilance
    Scott A. Malec, Assaf Gottlieb, Elmer Victor Bernstam, Trevor Cohen · 2018 · EasyChair preprint
  9. A Clinical Phenotyping Algorithm to Identify Cases of Chronic Obstructive Pulmonary Disease in Electronic Health Records
    Victoria L. Martucci, Nancy Liu, Vern Eric Kerchberger, Travis John Osterman, Eric S. Torstenson, Bradley W. Richmond, Melinda C. Aldrich · 2019 · bioRxiv (Cold Spring Harbor Laboratory)
  10. Utilizing Electronic Dental Record Data to Track Periodontal Disease Change
    Jay Sureshbhai Patel · 2020 · IUScholarWorks (Indiana University)
  11. Adjusting for the progressive digitization of health records: working examples on a multi-hospital clinical data warehouse
    Adam Remaki, Benoît Playe, Paul Bernard, Simon Vittoz, Matthieu Doutreligne, Gilles Châtellier, Étienne Audureau, Emmanuelle Kempf, Raphaël Porcher, Romain Bey · 2023 · medRxiv
  12. Development and validation of a patient-level model to predict dementia across a network of observational databases
    Luis H. John, Egill Axfjord Fridgeirsson, Jan A. Kors, Jenna Reps, Ross D. Williams, Patrick B. Ryan, Peter R. Rijnbeek · 2024 · BMC Medicine
  13. Ontology-driven identification of inconsistencies in clinical data: A case study in lung cancer phenotyping
    Yvon K. Awuklu, Fleur Mougin, R. Griffier, Meghyn Bienvenu, Vianney Jouhet · 2025 · Journal of Biomedical Informatics
  14. Using a statewide health information exchange to enhance COVID research and surveillance: The impact of information fragmentation
    Katie S. Allen, Seho Park, John Price, Xia Ning, Titus Schleyer · 2025 · International Journal of Medical Informatics
  15. Multicenter evaluation of machine and deep learning methods to predict glaucoma surgical outcomes
    Samuel Barry, Sophia Ying Wang · 2025 · Frontiers in Artificial Intelligence
  16. Developing a Suicide Risk Prediction Algorithm Using Electronic Health Record Data in Mental Health Care: Real-World Case Study
    Linda Hummel, Karin C A G Lorenz-Artz, Joyce J. P. A. Bierbooms, Inge M. B. Bongers · 2025 · JMIR Medical Informatics
  17. Developing the Interpretability of Deep Artificial Neural Network on Application Problems
    Sheng-An Yang, Meng-Han Yang · 2019 · International Conference on Machine Learning and Cybernetics
  18. Addressing persistent evidence gaps in cardiovascular sex differences research – the potential of clinical care data
    Sophie H. Bots, N. Charlotte Onland‐Moret, Hester M. den Ruijter · 2023 · Frontiers in Global Women s Health
  19. Automated Classification of Free-Text Radiology Reports: Using Different Feature Extraction Methods to Identify Fractures of the Distal Fibula
    Cornelia L. A. Dewald, Alina Balandis, Lena S. Becker, Jan Bernd Hinrichs, Christian von Falck, Frank K. Wacker, Hans Laser, Svetlana Gerbel, Hinrich Boy Winther, Johanna Apfel-Starke · 2023 · RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren
  20. Early Ascertainment of Breast Cancer Diagnoses Comparing Self-Reported Questionnaires and Electronic Health Record Data Warehouse: The WISDOM Study
    Katherine Leggat-Barr, Rita H. Ryu, Michael A. Hogarth, Allison Stover Fiscalini, Laura van ‘t Veer, Hannah Lui Park, Tomiyuri Lewis, Caroline A. Thompson, Alexander D. Borowsky, Robert A. Hiatt et al. · 2023 · JCO Clinical Cancer Informatics
  21. Using Continuous Glucose Monitoring Values for Bolus Size Calculation in Smart Multiple Daily Injection Systems: No Negative Impact on Post-bolus Glycemic Outcomes Found in Real-World Data
    Franck Diaz‐Garelli, Aakash Shah, Arthur Mikhno, Pratik K. Agrawal, Amanda K. Kinnischtzke, Robert Alan Vigersky · 2023 · Journal of Diabetes Science and Technology
  22. “Goldmine” or “big mess”? An interview study on the challenges of designing, operating, and ensuring the durability of Clinical Data Warehouses in France and Belgium
    Sonia Priou, Emmanuelle Kempf, Marija Janković, Guillaume Lamé · 2024 · Journal of the American Medical Informatics Association
  23. Estimating the observability of an outcome from an electronic health record data set using external data
    Mengying Yan, Hwanhee Hong, Jonathan A. Wilson, Benjamin Alan Goldstein · 2025 · American Journal of Epidemiology
  24. Sex- and age-specific differences in the associations between comorbidity and incident heart failure
    Weida Qiu, Anping Cai, Shiping Wu, Yanchen Zhu, He Zheng, Yingqing Feng · 2025 · QJM
  25. Overcoming data challenges through enriched validation and targeted sampling to measure whole-person health in electronic health records
    Sarah C. Lotspeich, S. Kedar, Rabeya Tahir, Aidan Keleghan, Amelia Miranda, Stephany N. Duda, Michael P. Bancks, Brian J. Wells, Ashish Kumar Khanna, Joseph Rigdon · 2025 · Journal of Biomedical Informatics
  26. Sekundärnutzung klinischer Daten in datensammelnden, nicht-interventionellen Forschungs- oder Lernaktivitäten – Begriff, Studientypen und ethische Herausforderungen
    Martin Jungkunz, Anja Köngeter, Eva Caroline Winkler, Katja Mehlis, Christoph Schickhardt · 2021 · Springer eBooks
  27. Information Technology for Clinical, Translational and Comparative Effectiveness Research
    Rémy Choquet, Christel Daniel, Section Editors for the IMIA Yearbook Section on Section on Clinical Research Informatics · 2014 · Yearbook of Medical Informatics
  28. Dramatyping: a generic algorithm for detecting reasonable temporal correlations between drug administration and lab value alterations
    Axel Newe · 2016 · PeerJ
  29. Warfarin Dose Estimation on High-dimensional and Incomplete Data
    Zeyuan Wang, Josiah Poon, Jie Yang, Simon Kar-Sing Poon · 2021 · Hawaii International Conference on System Sciences (HICSS)
  30. Exploring the Hazards of Scaling Up Clinical Data Analyses: A Drug Side Effect Discovery Case Report.
    Franck Diaz‐Garelli, Todd R. Johnson, Mohammad H. Rahbar, Elmer Victor Bernstam · 2021 · PubMed Central
  31. Supplementing systematic review findings with healthcare system data: pilot projects from the Agency for Healthcare Research and Quality Evidence-based Practice Center program
    Haley K Holmer, Suchitra Iyer, Celia V. Fiordalisi, Edi Kuhn, Mary L Forte, Mohammad Hassan Murad, Zhen Wang, Amy Y. Tsou, Jeremy J. Michel, Craig A. Umscheid · 2024 · Journal of Clinical Epidemiology
  32. Enhancing the Representational Power of i2b2 through Referent Tracking.
    Jonathan C Blaisure, Werner M Ceusters · 2018 · Europe PMC (PubMed Central)
  33. Aligning an Administrative Procedure Coding System with SNOMED CT.
    Stefan Schulz, Johannes Steffel, Peter Polster, Matvey B. Palchuk, Philipp Daumke · 2019 · JOWO
  34. Developing a Data-driven Medication Indication Knowledge Base using a Large Scale Medical Claims Database.
    Ying Li, Cao Xiao · 2019 · PubMed Central
  35. Agreement between blood pressure from research study visits versus electronic medical records and associations with hypertensive disorder diagnoses in pregnant women with overweight/obesity
    A. Lane-Cordova, S. Wilcox, B. Fernhall, Ji-Hong Liu · 2021 · Blood Pressure Monitoring
  36. Paperwork
    Joshua B. Barbour · 2019 · Health Communication
  37. Research in health information management: An expanding field of enquiry
    Joan Henderson · 2017 · Health Information Management Journal
  38. Federated machine learning with Anonymous Random Hybridization (FeARH) on medical records
    Jianfei Cui, Zhu, He, Deng, Hao, Ziwei Chen, Dianbo Liu · 2019 · arXiv (Cornell University)
  39. Analysis of Healthcare Systems Using Computational Approaches
    Hemanta Kumar Bhuyan, Subhendu Kumar Pani · 2022
  40. Levels of Electronic Health Records (EHR) Implementation and their Influence on Quality and Safety (Preprint)
    William Opoku-Agyeman · 2023
  41. Effect of vaccination on time till Long COVID, a comparison of two ways to model effect of vaccination and two outcome definitions
    Peter D. Smits, Patricia J Rodriguez, Samuel Gratzl, Brianna M Goodwin Cartwright, Sarah Gilson, Ryan H. Lee, Charlotte Baker, Nicholas L Stucky · 2023 · medRxiv
  42. Social Work Research Using Electronic Health Records and Criminal Justice Data: Recommendations and Lessons Learned
    Briana Barocas, Rei Shimizu, Sejung Yang · 2022 · Journal of the Society for Social Work and Research
  43. Informatics hygiene to support reuse of routinely collected health care data for evidence-based practice
    Elmer Victor Bernstam, Alejandro Araya, Matthew Decaro, Todd R. Johnson · 2024 · BMJ Evidence-Based Medicine
  44. A retrospective analysis of a clinician-initiated high-intensity locomotor training implementation project in an inpatient rehabilitation facility
    Annie Tapp, Daniel Dray, David Griswold, Richard Haybarger, Kenneth E. Learman · 2024 · Physiotherapy Theory and Practice
  45. A multifaceted approach to advancing data quality and fitness standards in multi-institutional networks
    Hanieh Razzaghi, Kimberley Dickinson, Kaleigh Wieand, Samuel Boss, Hunter Weidlich, Yungui Huang, Keith Morse, Sujan Kumar Mutyala, Jyothi Priya Alekapatti Nandagopal, Karthik Viswanathan et al. · 2025 · Journal of the American Medical Informatics Association
  46. Evaluation of electronic health record to HL7® FHIR® mappings in pediatric research studies
    Maryam Y. Garza, Zhan Wang, Bhargav Adagarla, Michael Rutherford, Ümit Topaloĝlu, D. K. Benjamin, Kanecia Obie Zimmerman, Eric L. Eisenstein, Karan R. Kumar · 2026 · International Journal of Medical Informatics
  47. Assessment of the integrity of real-time electronic health record data used in clinical research
    Jessica Liu, Sameer Pandya, Andreas C. Coppi, H. Patrick Young, Harlan M. Krumholz, Wade L. Schulz, Guannan Gong · 2026 · PLoS ONE
  48. Natural language processing to enhance rheumatoid arthritis care in clinical studies: a scoping review of applications, data, approaches, challenges and future directions
    Yinan Huang, Sandeep Krishna Agarwal · 2026 · Rheumatology International
  49. PDA (Privacy-Preserving Distributed Algorithms) in action: ten principles for high-quality multi-site clinical evidence generation
    Yong Chen, Jiayi Tong, Yiwen Lu, Rui Duan, Chongliang Luo, Marc A. Suchard, Patrick B. Ryan, Andrew E. Williams, J H Holmes, Jason H. Moore et al. · 2026 · Journal of the American Medical Informatics Association
  50. Leveraging domain knowledge to facilitate visual exploration of large population datasets.
    William W.Y. Hsu, Alex A. T. Bui · 2013 · Europe PMC (PubMed Central)
  51. Future Directions for Translational Informatics
    Peter J. Embí, Philip Payne · 2014 · Health informatics
  52. Normalization of Phenotypic Data from a Clinical Data Warehouse: Case Study of Heterogeneous Blood Type Data with Surprising Results
    James J. Cimino · 2015 · Studies in health technology and informatics
  53. Successful System, Incomplete Data: Caveats in Reusing Activity Data from Emergency Department Whiteboards
    Morten Hertzum · 2017 · Studies in health technology and informatics
  54. Billing and Review Perspectives in Healthcare
    Joel Fredrickson · 2019 · Advances in healthcare information systems and administration book series
  55. Documentation of Sleep Hygiene With Melatonin Use in Management of Sleep Disturbance in Children With Neurodevelopmental Disorders: A Quality Improvement Project
    Stephanie Hosley, Christine A. Fortney, Tondi M. Harrison, Deborah K. Steward · 2021 · Journal of Pediatric Health Care
  56. Associations between Florida counties’ COVID-19 case and death rates and meaningful use among Medicaid providers: Cross-sectional ecologic study
    Katherine D Freeman, Judith P. Monestime · 2022 · PLOS Digital Health
  57. "In conferences, everyone goes 'health data is the future' ": an interview study on challenges in re-using EHR data for research in Clinical Data Warehouses.
    Sonia Priou, Guillaume Lamé, Marija Janković, Emmanuelle Kempf · 2023 · PubMed Central
  58. Noncutaneous Infections in Patients with Hidradenitis Suppurativa: A Retrospective Cohort Study
    Bruna Galvao de Oliveira Wafae, Alexandra Philippa Charrow, Megan H. Noe · 2025 · JID Innovations
  59. The Importance and Use of Electronic Health Records in Clinical Research
    Jon W McKeeby, Patricia S. Coffey · 2017 · Elsevier eBooks
  60. Analysing health data sources to inform chronic disease management decisions of health insurers: A mixed methods study
    Joanna Khoo, Helen M. Hasan · 2018 · Informatics for Health and Social Care
  61. Evaluation of the accuracy of algorithms to identify soft tissue sarcoma (STS) in administrative claims
    Nicole Princic, Donna McMorrow, Philip Chan, Lisa M. Hess · 2020 · Clinical Sarcoma Research
  62. Precision Medicine and a Learning Health System for Mental Health
    Piper A. Ranallo, Jessica D. Tenenbaum · 2021 · Health informatics
  63. Developing a Data Quality Standard Primer for Cardiovascular Risk Assessment from Electronic Health Record Data Using the DataGauge Process.
    Franck Diaz‐Garelli, Andrew Long, Michael P. Bancks, Alain Gerald Bertoni, Adhithya Narayanan, Brian J. Wells · 2021 · PubMed Central
  64. Medication based machine learning to identify subpopulations of pediatric hemodialysis patients in an electronic health record database
    Autumn M. McKnite, Kathleen M. Job, Raoul D. Nelson, Catherine M.T. Sherwin, Kevin Watt, Simon Brewer · 2022 · Informatics in Medicine Unlocked
  65. Embracing National Cancer Registries for Improved Care of Rare Tumors
    David F. Schneider · 2014 · Annals of Surgical Oncology
  66. Quality Management Using Data Analytics: An Application to Pharmaceutical Regulation
    Vishal Ahuja, John R. Birge, Chad Syverson, Elbert S. Huang, Min‐Woong Sohn · 2015 · SSRN Electronic Journal
  67. Commentary on Winhusen et al . (2019): Substance use disorders, chronic diseases, and electronic health records—a paradigm for screening and intervention
    Paolo Mannelli, Li-Tzy T. Wu · 2019 · Addiction
  68. Apples and Oranges? Considerations for EHR-Based Analyses Aggregating Data From Interventional Clinical Trials and Point-of-Care Encounters in Oncology
    Jessica A. Lavery, Margaret K. Callahan, Katherine S. Panageas · 2021 · JCO Clinical Cancer Informatics
  69. Use of Recommended Real-World Methods for Electronic Health Record Data Analysis Has Not Improved Over 10 Years
    Chenyu Li, Abdulrahman M. Alsheikh, Karen A. Robinson, Harold P. Lehmann · 2023 · medRxiv
  70. Challenges and Opportunities for Secondary Use of Observational Data Following an EHR Transition
    Michael Edwin Matheny, Hannah M. Gelman, Maria Souden, Zhenyu Lu, Scott L. DuVall, Margaret E. Gonsoulin · 2023 · Journal of General Internal Medicine
  71. Automated Tailoring of Clinical Performance Feedback in Low-Resource Settings
    Landis Lewis, J Zachary · 2014 · D-Scholarship@Pitt (University of Pittsburgh)
  72. Toward a Generalized Model of Biomedical Query Mediation to Improve Electronic Health Record Data Retrieval
    Gregory W. Hruby · 2016
  73. DataGauge: A Model-Driven Framework for Systematically Assessing the Quality of Clinical Data for Secondary Use
    Jose Franck DiazVasquez · 2016 · Digital Commons-TMC (Texas Medical Center)
  74. A MVC based User Interface Design for Clinical Research Data Extraction
    Cheng Yi Yang, Callum Young, Chien‐Tsai Liu · 2015
  75. Using the Literature to Identify Confounders
    Scott A. Malec · 2018 · EasyChair preprint
  76. Healthcare utilization and costs with fixed-source versus variable-source tacrolimus in patients receiving a kidney transplant
    Suvapun Bunniran, Edward Wolfgang Lee, Pravin Kamble, Brandon T. Suehs, Billy Franks, Jason J. Schwartz, Gary D. Thal, James Robert Spalding · 2018 · Journal of Medical Economics
  77. PROPOSTA DE MODELO DE BANCO DE DADOS DISTRIBUÍDO PARA O PRONTUÁRIO ELETRÔNICO ÚNICO DO PACIENTE
    José da Silva Azanha Neto, Débora Vigilia Canne, Luis Antônio Coppa Ybarra, Antônio Andrade dos Santos, Jorge R. B. Garay, Sérgio Takeo Kofuji · 2018 · South American Development Society Journal
  78. A Practice-Based Evidence Approach For Clinical Decision Support
    Hamzah Osop · 2018 · Queensland University of Technology
  79. Synchronization of Machine Learning into Electronic Health Records
    N. Meet, Eshan Vatsa, Sumathi K Nitin · 2019 · International Journal of Computer Applications
  80. Reinventing Electronic Health Records During COVID-19: Better Patient Data and Faster Research by Restructuring Electronic Health Record Systems
    John Yeh, Mary J. Yeh · 2020 · Current Women s Health Reviews
  81. Catch Me if You Can: Acute Events Hidden in Structured Chronic Disease Diagnosis Descriptions Show Detectable Recording Patterns in EHR.
    Franck Diaz‐Garelli, Kristin Macfarlane Lenoir, Brian J. Wells · 2020 · PubMed Central
  82. Safety and efficacy of cardiovascular medication in women and men; the added value of clinical care data
    Sophie H. Bots · 2021
  83. Analysis of Error-prone Electronic Health Records with Multi-wave Validation Sampling: Association of Maternal Weight Gain during Pregnancy with Childhood Outcomes
    Bryan E. Shepherd, Kyunghee Han, Tong Chen, Aihua Bian, Shannon Pugh, Stephany N. Duda, Thomas Lumley, William J. Heerman, Pamela A. Shaw · 2021 · arXiv (Cornell University)
  84. Profil Penggunaan Antibiotik pada Pasien Klinik Anak di Rumah Sakit MM Indramayu Periode Januari-Maret 2021
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  85. Faculty Opinions recommendation of Bayesian analysis of genetic association across tree-structured routine healthcare data in the UK Biobank.
    Spiros Denaxas · 2018 · Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature
  86. Peer Review #2 of "Dramatyping: a generic algorithm for detecting reasonable temporal correlations between drug administration and lab value alterations (v0.1)"
    2016 · PeerJ
  87. Peer Review #1 of "Dramatyping: a generic algorithm for detecting reasonable temporal correlations between drug administration and lab value alterations (v0.1)"
    2016 · PeerJ
  88. Peer Review #2 of "Dramatyping: a generic algorithm for detecting reasonable temporal correlations between drug administration and lab value alterations (v0.2)"
    2016 · PeerJ
  89. A Smart and User-Friendly Interface for Storing and Retrieving Personal Medical Records
    G Swathi, H. Rakshana, T.M. Usha Mary · 2022 · SSRN Electronic Journal
  90. Delivering adaptive online learning using electronic health data: A feasibility and acceptability study with emergency trainees
    Anna L. Janssen, Andrew Coggins, James H Tadros, Deleana Quinn, Amith Shetty, Tim J Shaw · 2023 · Research Square
  91. Accelerating data-driven discover in type 1 diabetes: an informatics-based approach
    Erin M. Tallon · 2022 · MOspace Institutional Repository (University of Missouri)
  92. Artificial intelligence in head neck cancer full of potential BUT filled with landmines
    Shrikant Balasaheb Mali, Sachinkumar Dattatray Dahivelkar, GL Pradeep · 2023 · Oral Oncology Reports
  93. Establishing Trust in Pharmaceutical Data with an Independent Verification and Validation Methodology.
    Keith E. Campbell, Taima Gomez, Elizabeth D Korte, Raja A. Cholan, Greg Rehwoldt, Andrew K Sills, Christine Spisla, Traci Hindman Robinson, Philip J. Meacham, Alicia Bracco et al. · 2022 · PubMed Central
  94. Data Imputation and Domain Adaptative Prediction of One-Year Postoperative Mortality in Geriatric Hip Fracture Patients from Multi-Hospitals
    Xingchen Lu, Cong Zeng, Xinyu Liu, Ning Hu, Jingjing Xiao, Yan Xiong · 2024 · SSRN Electronic Journal
  95. Partition-Based Technique to Enhance Missing Data Prediction
    Mohammad Mahdi Barati Jozan, Hamed Tabesh · 2024 · Indonesian Journal of Electrical Engineering and Informatics (IJEEI)
  96. THE ROLE OF HEALTHCARE TECHNOLOGY IN IMPROVING PATIENT SAFETY
    Amal Ahmed Alqadi, Haytham Abdulsalam Nasrulden, Mohammed Hashem A Al Abdulmohsen, Mohammed Abdulkarim M ‏Al Suliman, Mohammed Saleh Butayban, Ahmed Taher Al Sayafi, Shada Murshed Alharbi, Wedad Ayed Al Mutari, Dalia Salem Sageer, Ebtihal Abdrabalnabi A Alfashkhi et al. · 2022 · Journal of Population Therapeutics and Clinical Pharmacology
  97. EXAMINING THE COMPARATIVE EFFECTIVENESS AND SAFETY OF TOPIRAMATE AND LAMOTRIGINE MONOTHERAPY IN THE TREATMENT OF MIGRAINE
    Rakan Alotaibi, Mutaz Yaslam Alsaiari, Hussain Mansour Alharthi, Mohammed Abdullah Alasmari, Ali Saad Alshahrani, soltan aodalah Aljoed, Yousef Ruddah Aljabri, Mohamed salman alamri · 2022
  98. Factors Associated with Substance Use Disorder among High-Need Adolescents and Young Adults in North Carolina
    Phillip M. Hughes, Izabela E. Annis, Neal A. deJong, Robert B. Christian, Scott Davis, Kathleen C. Thomas · 2024 · North Carolina Medical Journal
  99. Using electronic health data to deliver an adaptive online learning solution to emergency trainees: A pilot study (Preprint)
    Anna L. Janssen, Andrew Coggins, James H Tadros, Deleana Quinn, Amith Shetty, Tim J Shaw · 2024
  100. Rethinking Research
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