February 19, 2022

Multiple studies have found that 10% to 12% of hospitalized patients experience adverse events, with approximately half of these events considered preventable. The prevalence of preventable adverse events has not been as extensively studied in other health care settings, but a growing body of research documents that preventable harm is common in all sites of care. Most health care is delivered in the outpatient setting, and studies of outpatients have shown comparable rates of harm to those in hospitalized patients. Recent studies analyzing harm in Medicare patients in long-term care and rehabilitation hospitals have also found that more than 10% of patients in these settings experience adverse events. It has also been well documented that transitions of care are particularly risky, especially after hospital discharge.

What Is Patient Safety?

The patient safety field uses the term adverse events to describe patient harm that arises as a result of medical care (rather than from the underlying disease). Important subcategories of adverse events include:

  • Preventable adverse events: those due to error or failure to apply an accepted strategy for prevention;
  • Ameliorable adverse events: events that, while not preventable, could have been less harmful if care had been different;
  • Adverse events due to negligence: those due to care that falls below the standards expected of clinicians in the community.

Two other terms are used to describe hazards to patients that do not result in harm:

  • Near miss: an unsafe situation that is indistinguishable from a preventable adverse event except for the outcome. A patient is exposed to a hazardous situation but does not experience harm (either through luck or early detection).
  • Error: a broader term referring to any act of commission (doing something wrong) or omission (failing to do the right thing) that exposes patients to a potentially hazardous situation.

The National Patient Safety Foundation issued its Free From Harm report in 2015. Acknowledging these and other challenges to the safety field, the report made eight key recommendations to ensure continued progress in the safety field:

  • Ensure that leaders establish and sustain a safety culture
  • Create centralized and coordinated oversight of patient safety
  • Create a common set of safety metrics that reflect meaningful outcomes
  • Increase funding for research in patient safety and implementation science
  • Address safety across the entire care continuum
  • Support the health care workforce
  • Partner with patients and families for the safest care
  • Ensure that technology is safe and optimized to improve patient safety

There is now a general consensus that the patient safety field should shift from focusing on single types of adverse events, and instead emphasize designing safer systems of care. This shift is based on the recognition that unsafe systems put patients at risk of multiple different types of adverse events simultaneously.


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