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It had been 30 years since the Harvard Medical Practice Study had been done, and ...I was surprised that the overall rates were as high as they were.

David Bates, MD

Chief of the Department of General Internal Medicine, Brigham and Women’s Hospital

A new study that looks at when, where, and how medical errors occur in the in-patient setting is shining a bright light on threats to patient safety and quality in health care. A topline result of a 25 percent error rate for hospital admissions is getting a lot of attention. The 1991 Harvard Medical Study found only three to four percent, giving rise to the patient safety movement. David Bates and colleagues’ research in the New England Journal of Medicine in early 2023, titled The Safety of Inpatient Health Care, indicates that, far from solving the problem, the patient safety movement still has a long way to go.

“It had been 30 years since the Harvard Medical Practice Study had been done, and we wanted to do several things.”

Dr. David Bates is a practicing internist and Chief of the Department of General Internal Medicine at Brigham and Women’s Hospital in Boston. His seminal research into drug-related injuries and care redesign has led many in health care to focus on systems and computerized improvements. In the new study, significant changes in the methodology make a head-to-head comparison with the Harvard Medical Practice Study challenging. How care is delivered and patient acuity has changed too. The goals of this study were to measure the frequency and type of harm in the various settings and test some electronic tools for identifying errors. Some of the findings were unexpected.

“There were a couple of things that surprised me. I was surprised that the overall rates were as high as they were. They were around three to four percent in the original study and we found that nearly a quarter of the patients suffered an adverse event during hospitalization in this study. I expected it to be higher than three or four percent, but I didn’t expect it to be quite as high as it was.”

Most facilities use EMRs today, and Dr. Bates says that the study’s expanded use of triggers may have detected more errors. Researchers examined electronic medical records from inpatient admissions in 2018 at 11 hospitals from three health systems. They represented large and small facilities from fewer than 100 beds to more than 700. Reviewers used triggers known to flag potential errors. The study concluded that nearly a quarter of the errors were preventable; among those, one-fifth were serious; three percent were life-threatening; and 0.5 percent were fatal. Adverse drug events were most frequent, followed by surgical errors, and then procedural events.

Another surprise for Dr. Bates was that diagnosis-related errors were not more prevalent in the data. He suggests that the trigger methodology may miss many inpatient diagnostic errors, which his other recent research has found to be reasonably frequent.

Pat Folcarelli is Vice President of Patient Safety at CRICO, Harvard’s medical malpractice and patient safety company, and a study co-author. CRICO helped sponsor the research.

“The reason for doing it is to see have we gotten better? Weve done a lot of interventions to improve patient safety and to reduce risk for our patients. And there was an interest in seeing, okay, where are we now with this current state of the way we deliver care, and what can we improve?

Folcarelli says she didn’t expect that medication-related errors would be the most prevalent, at 39 percent. But compared with the original Harvard study, the new methodology picked up additional types of drug-related harms.

“I think in patient safety we’ve done a lot to improve medication safety, in terms of the prescribing practices that are now usually electronic, and then we have bar-coded administration systems, but there are other harms that patients experience from medication: low blood pressure that’s too low after a medications given, changes in their mental status, injury to their kidneys. This study captured all of those kinds of injuries from medications, and so I think we have work to do around medication safety.

“The patients are more complex now that are hospitalized, so theyre on a lot of medications, and the medications have interactions, and there can be insidious changes over time in the patients response to the medication, and thats harm from the patients perspective. And I think we need to look harder at our systems for monitoring patients who are on medications.”

Study co-author, Dr. Elizabeth Mort, sees the results as a call to arms for hospitals across the country. Dr. Mort is Senior Vice President of Quality and Safety at Massachusetts General Hospital.

“If not now, when? We have to get going! But theres a lot of options out there, and I think the call to action will hopefully motivate people to look at the options, pick strategically, and implement with the goal of measuring something that suggests you’re making progress. Where I have optimism about that—and this is the emphasis I would make to provider groups, or anybody who’s involved in either delivering or getting care—is that there are many, many things that we can do to get back on track and to reduce the risk of preventable patient harms.”

Dr. Mort emphasizes the challenge for the board and senior management at hospitals: maintaining a consistent focus and priority on patient safety and quality—all while staring down the fundamental staffing and operational pressures that have emerged from the pandemic. To help prioritize, leaders can look at this research and similar guidance from the Office of Inspector General, CMS, and the Agency for Healthcare Research and Quality. According to Dr. Bates, the study clearly points to medication safety because drug events were the top category of inpatient error.

“So for adverse drug events, the most obvious opportunity for improvement is to do better with a medication related to decision support that were delivering now. The evidence is that the decision support thats being currently delivered in most institutions is just not very good. Doctors are being bombarded with warnings, most of them are not that helpful, and there are opportunities to be much more selective about which warnings to actually deliver so that you just deliver the most important ones. And I think if that’s done better, this remains to be tested, we'll see a significant improvement in medication safety.”

Dr. Bates says it helps to look at a variety of higher-priority categories of adverse events for action: surgical checklists and early-recovery-after-surgery programs, for example. For slips and falls, certain protocols and tools are demonstrated to make care safer but have not been adopted widely enough. New techniques to prevent error are coming online all the time.

“For some other types of injuries, like pressure ulcers, I think artificial intelligence will be really useful, in terms of prevention, or others like identifying patients who are decompensating. I think that use of artificial intelligence to look at multiple parameters at the same time will help us identify patients who are not doing well and ideally intervene before they actually get worse. There are some data from Kaiser that if you do that just with vital signs, that actually reduces the mortality rate.”

To Pat Folcarelli of CRICO, AI holds a lot of promise for flagging potential harms and helping improvement efforts. She also sees the need for additional collaboration. The study showed that many errors are missed by the hospital’s self-reporting system of tracking events. New improvements are needed for systems around detection, measurement, definitions of harm, and preventability that help providers understand the patient experience. 

Dr. Mort says medical error is everybody’s problem to solve.

“Quality and safety is not one person’s role, or one center’s role, its really everybody’s role. And I think wed be well served at pausing and asking each one of the leaders in the C-Suite, in the clinical departments, in the operational departments, really from board to bedside, what is your role in advancing patient safety? You might be an MRI tech, you might be the director of environmental services, you might be a resident or a fellow in radiation oncology, you might be a primary care doc, you might be the chief operating officer, what is your role in advancing patient safety? And if you do this, you can say, ‘well, Im an environmental service worker, and my role is to ensure when I clean the rooms between patients that I eradicate to the extent possible all germs that can hurt the patient,’ or whatever way the person would want to articulate that. And that’s why they come to work, thats why they're there. ‘Yes, I'm in environmental services, and thats how I contribute to making this place the safest hospital on the planet.’ ”

Evaluation of medical error in ambulatory care is in the works, according to Dr. Bates. Also among his upcoming projects will be to look at effective ways to get information from detection systems directly to front-line providers in real time, and better, faster detection of diagnostic error.

For Safety Net, I’m Tom Augello.


  • David Bates, MD
  • Pat Folcarelli, PhD, RN
  • Elizabeth Mort, MD, MPH
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