From the Journals

Adverse events reported in one-quarter of inpatient admissions



Nearly 25% of hospital admissions included at least one adverse event, as indicated from data from 2,809 admissions at 11 hospitals.

The 1991 Harvard Medical Practice Study, which focused on medical injury and litigation, documented an adverse event rate of 3.7 events per 100 admissions; 28% of those events were attributed to negligence, write David W. Bates, MD, of Brigham and Women’s Hospital, Boston, and colleagues.

Although patient safety has changed significantly since 1991, documenting improvements has been challenging, the researchers say. Several reports have shown a decrease in health care–associated infections. However, other aspects of safety – notably, adverse drug events, defined as injuries resulting from drugs taken – are not easily measured and tracked, the researchers say.

“We have not had good estimates of how much harm is being caused by care in hospitals in an ongoing way that looked across all types of adverse events,” and the current review is therefore important, Dr. Bates said in an interview.

In a study recently published in the New England Journal of Medicine, the researchers analyzed a random sample of 2,809 hospital admissions from 11 hospitals in Massachusetts during the 2018 calendar year. The hospitals ranged in size from fewer than 100 beds to more than 700 beds; all patients were aged 18 years and older. A panel of nine nurses reviewed the admissions records to identify potential adverse events, and eight physicians reviewed the adverse event summaries and either agreed or disagreed with the adverse event type. The severity of each event was ranked using a general severity scale into categories of significant, serious, life-threatening, or fatal.

Overall, at least one adverse event was identified in 23.6% of the hospital admissions. A total of 978 adverse events were deemed to have occurred during the index admission, and 222 of these (22.7%) were deemed preventable. Among the preventable adverse events, 19.7% were classified as serious, 3.3% as life-threatening, and 0.5% as fatal.

A total of 523 admissions (18.6%) involved at least one significant adverse event, defined as an event that caused unnecessary harm but from which recovery was rapid. A total of 211 admissions involved a serious adverse event, defined as harm resulting in substantial intervention or prolonged recovery; 34 included at least one life-threatening event; and seven admissions involved a fatal adverse event.

A total of 191 admissions involved at least one adverse event deemed preventable. Of those, 29 involved at least one preventable adverse event that was serious, life-threatening, or fatal, the researchers write. Of the seven deaths in the study population, one was deemed preventable.

The most common adverse events were adverse drug events, which accounted for 39.0% of the adverse events; surgical or other procedural events accounted for 30.4%; patient care events (including falls and pressure ulcers) accounted for 15.0%; and health care–associated infections accounted for 11.9%.

Overcoming barriers to better safety

“The overall level of harm, with nearly 1 in 4 patients suffering an adverse event, was higher than I expected it might be,” Dr. Bates told this news organization. However, techniques for identifying adverse events have improved, and “it is easier to find them in electronic records than in paper records,” he noted.

“Hospitals have many issues they are currently dealing with since COVID, and one issue is simply prioritization,” Dr. Bates said. “But it is now possible to measure harm for all patients using electronic tools, and if hospitals know how much harm they are having in specific areas, they can make choices about which ones to focus on.”

“We now have effective prevention strategies for most of the main kinds of harm,” he said. Generally, rates of harm are high because these strategies are not being used effectively, he said. “In addition, there are new tools that can be used – for example, to identify patients who are decompensating earlier,” he noted.

As for additional research, some specific types of harm that have been resistant to interventions, such as pressure ulcers, deserve more attention, said Dr. Bates. “In addition, diagnostic errors appear to cause a great deal of harm, but we don’t yet have good strategies for preventing these,” he said.

The study findings were limited by several factors, including the use of data from hospitals that might not represent hospitals at large and by the inclusion mainly of patients with private insurance, the researchers write. Other limitations include the likelihood that some adverse events were missed and the level of agreement on adverse events between adjudicators was only fair.

However, the findings serve as a reminder to health care professionals of the need for continued attention to improving patient safety, and measuring adverse events remains a critical part of guiding these improvements, the researchers conclude.

Timely reassessment and opportunities to improve

In the decades since the publication of the report, “To Err Is Human,” by the National Academies in 2000, significant attention has been paid to improving patient safety during hospitalizations, and health care systems have increased in both system and disease complexity, Said Suman Pal, MBBS, a specialist in hospital medicine at the University of New Mexico, Albuquerque, said in an interview. “Therefore, this study is important in reassessing the safety of inpatient care at the current time,” he said.

“The findings of this study showing preventable adverse events in approximately 7% of all admissions; while concerning, is not surprising, as it is consistent with other studies over time, as the authors have also noted in their discussion,” said Dr. Pal. The current findings “underscore the importance of continuous quality improvement efforts to increase the safety of patient care for hospitalized patients,” he noted.

“The increasing complexity of medical care, fragmentation of health care, structural inequities of health systems, and more recent widespread public health challenges such as the COVID-19 pandemic have been, in my opinion, barriers to improving patient safety,” Dr. Pal said. “The use of innovation and an interdisciplinary approach to patient safety and quality improvement in hospital-based care, such as the use of machine learning to monitor trends and predict the individualized risk of harm, could be a potential way out” to help reduce barriers and improve safety, he said.

“Additional research is needed to understand the key drivers of preventable harm for hospitalized patients in the United States,” said Dr. Pal. “When planning for change, keen attention must be paid to understanding how these [drivers] may differ for patients who have been historically marginalized or are otherwise underserved so as to not exacerbate health care inequities,” he added.

The study was funded by the Controlled Risk Insurance Company and the Risk Management Foundation of the Harvard Medical Institutions. Dr. Bates owns stock options with AESOP, Clew, FeelBetter, Guided Clinical Solutions, MDClone, and ValeraHealth and has grants/contracts from IBM Watson and EarlySense. He has also served as a consultant for CDI Negev. Dr. Pal has disclosed no relevant financial relationships.

A version of this article first appeared on

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