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Errors are inevitable in the practice of medicine. The most obvious causes are failures in individual performance related to attention, memory, knowledge, judgment, skill, and motivation. However, they also result in part from the nature of medical work, such as the complexity of medical knowledge, the uncertainty of clinical predictions, and the need to make timely treatment decisions in spite of limited or uncertain knowledge. And importantly, mistakes are caused by system factors that influence working conditions. Although much attention has been focused on the harmful effects of errors on patients, it must be understood that these incidents can be correspondingly distressing for physicians, evoking shock and feelings of remorse, guilt, anger, and fear.

If dealt with effectively, errors can provide powerful learning experiences for physicians; however, difficulty in dealing with mistakes may impede both learning and efforts to prevent future errors. Professional norms that assume physician infallibility and treat mistakes as anomalies pose significant barriers to learning. Judgmental institutional responses and fear of litigation are further disincentives to the open discussion of mistakes and reduce the potential for wider learning.


It is useful to define several terms related to what are commonly referred to as errors or mistakes. The Institute of Medicine (IOM) defines an error as “the failure of a planned action to be completed as intended (i.e., error of execution), or the use of a wrong plan to achieve an aim (i.e., error of planning). An error may be an act of commission or an act of omission.” An adverse event is an injury due to health care. Errors differ from adverse events because they do not necessarily cause harm. They differ from negligence or malpractice, which require both preventable harm and violation of the standard of practice.


Most studies of medical errors have focused on the hospital setting and on adverse events. Although the overall prevalence of errors is difficult to ascertain, it appears that they are common. Studies conducted in multiple states and countries suggest that the rate of adverse events may be as high as 10%. The Canadian Adverse Events Study reported on the incidence of adverse events among hospital patients in Canada. The authors randomly selected four hospitals (one teaching, one large community, and two small community hospitals) in each of five Canadian provinces and reviewed a random sample of charts for nonpsychiatric, nonobstetric adult patients hospitalized in each hospital during 2000. Trained reviewers screened all eligible charts, and physicians reviewed the positively screened charts to identify adverse events and to determine whether they were preventable. After adjustment for sampling, the adverse event rate was 7.5 per 100 hospital admissions (7.5%). Among the adverse events experienced by patients, 36.9% were judged to have been preventable; 20.8% of these preventable events resulted in death. According to the physician reviewers, the adverse events were associated ...

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