Any medical intervention such as a test, treatment, hospitalization or surgery can result in an undesirable outcome that is not caused by the underlying disease. Adverse events are common and have a wide range of severity, including death. They may be preventable or not preventable.
The term “adverse event” debuted in 1991 with the Harvard Medical Practice Study, which tried to measure the extent of malpractice in New York state hospitals. It defined an adverse event as “an unintended injury that was caused by medical management and that resulted in measurable disability.”
The HHS Office of the Inspector General, which studies harms from medical care, defines an adverse event as “an incident that prolonged a patient’s stay, caused permanent harm, required life-saving intervention or contributed to death.” That agency distinguishes an adverse event from a “temporary harm event,” which is harm from a medical intervention that did not prolong a patient’s hospital stay, require life-sustaining intervention, or cause lasting harm.
The vast majority of adverse events go undetected, which has led to the development of technology that can detect “triggers,” or clues that harm has occurred. Researchers are also working on systems to identify conditions under which adverse events occur in order to prevent them.