Categorization of Medication Safety Errors in Ambulatory Electronic Health Records


  • Karen Paul Zimmer, MD, MPH Jefferson Health
  • David C. Classen, MD, MS University of Utah
  • Jessica M. Cole, BS University of Utah



Preventable medication errors continue to affect the quality and consistency in the delivery of care. While numerous studies on medication safety have been performed in the inpatient setting, a review of ambulatory patient safety by the American Medical Association found that medication safety errors were the most frequent safety problems in the outpatient arena. The leading cause of ambulatory safety problems, adverse drug events (ADEs), are common, with estimates of more than 2 million ADEs each year in the ambulatory Medicare population alone, and these events are frequently preventable. We conducted an environmental scan that allowed us to create our own categorization schema of medication safety errors in electronic healthcare records (EHRs) found in the outpatient setting and observed which of these were additionally supported in the literature. This study combines data from the Collaborative Healthcare Patient Safety Organization (CHPSO), with several key articles in the area of medication errors in the EHR era.

Method: To best utilize the various EHR ambulatory medication events submitted into CHPSO’s database, we chose to create a framework to bucket the near misses or adverse events (AEs) submitted to the database. This newly created categorization scheme was based on our own drafted categorization labels of events, after a high-level review, and from two leading articles on physician order entry. Additionally, we conducted a literature review of computerized provider order entry (CPOE) medication errors in the ambulatory setting. Within the newly created categorization scheme, we organized the articles based on issues addressed so we could see areas that were supported by the literature and what still needed to be researched.

Results: We initially screened the CHPSO database for ambulatory safety events and found 25,417 events. Based on those events, an initial review was completed, and 19,242 events were found in the “Medication or Other Substance” and “Other” categories, in which the EHR appeared to have been a potential contributing factor. This review identified a subset of 2,236 events that were then reviewed. One hundred events were randomly selected for further review to identify common categories. The most common categories in which errors occurred were orders in order sets and plans (n=12) and orders crossing or not crossing encounters (n=12), incorrect order placed on correct patient (n=10), orders missing (n=8), standing orders (n=8), manual data entry errors (n=6), and future orders (n=6).

Conclusion: There were several common themes seen in this analysis of ambulatory medication safety errors related to the EHR. Common among them were incorrect orders consisting of examples such as dose errors or ordering the wrong medication. The manual data entry errors consisted of height or weight being entered incorrectly or entering the wrong diagnostic codes. Lastly, different sources of medication safety information demonstrate a diversity of errors in ambulatory medication safety. This confirms the importance of considering more than one source when attempting to comprehensively describe ambulatory medication safety errors.

Author Biographies

Karen Paul Zimmer, MD, MPH, Jefferson Health

Karen Paul Zimmer (, a pediatrician board certified in informatics, consults in the areas of health information technology (HIT), patient safety, and quality for nonprofit organizations, HIT companies, EHR vendors, and government agencies. She has over 25 years of combined experience with a focus on process improvement and strategic planning. Dr. Zimmer was formerly the medical director for the ECRI Institute Patient Safety Organization (PSO), as well as the medical director for the Patient Safety, Risk, and Quality Group. Her past works extend from implementation of IT and Quality Improvement (QI) programs at Johns Hopkins Hospital to leading government-sponsored HIT collaboratives. She is also an expert in evaluation processes, as she designed and studied a formal educational evaluation for pediatric residents at Johns Hopkins, where she held the rank of adjunct assistant professor in the Department of Pediatrics. Earlier in her career, she was involved in policy on the Clinton Health Care Task Force. She completed her term as a member of the National Quality Forum (NQF) Committee: HIT Patient Safety Measures Expert Panel. She is on the medical staff at Nemours/Alfred I. duPont Hospital for Children, an associate professor in the Department of Pediatrics at Thomas Jefferson University, and an instructor at the Jefferson College of Population Health.

David C. Classen, MD, MS, University of Utah

David C. Classen is a professor of Medicine at the University of Utah, a consultant in Infectious Diseases and Clinical Epidemiology at the University of Utah School of Medicine in Salt Lake City, and the chief medical information officer (CMIO) at Pascal Metrics. Dr. Classen developed the medication safety programs at Intermountain Healthcare, served as chair of the Intermountain Healthcare Clinical Quality Committee for Drug Use and Evaluation, and was also the initial developer of patient safety research at Intermountain Healthcare. In addition he developed, implemented, and evaluated a computerized physician order entry (CPOE) program at LDS Hospital that significantly improved the safety of medication use. He was a member of the Institute of Medicine Committee (IOM) that developed the National Quality Report on Health Care Delivery and was also a member of the IOM Committee on Patient Safety Data Standards. He was recently a member of the IOM Committee on Health Information Technology and Patient Safety. Dr. Classen is an advisor to the Leapfrog Group and has developed and implemented the CPOE/EHR flight simulator for the Agency for Healthcare Research and Quality (AHRQ) and the NQF. 

Jessica M. Cole, BS, University of Utah

Jessica M. Cole is a regulatory research coordinator (project manager) of the University of Utah Department of Internal Medicine and Division of Epidemiology. She began working at the University of Utah in 2009, supporting various roles within the School of Medicine. In 2017, she started her career path in research as a study coordinator and in two short years advanced from managing single-site projects to multisite projects. She currently supports projects within the University of Utah and the Veterans Administration (VA) Salt Lake City Health Care System.


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How to Cite

Zimmer, K. P., Classen, D. C., & Cole, J. M. (2021). Categorization of Medication Safety Errors in Ambulatory Electronic Health Records. Patient Safety, 3(1), 23–33.



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