The epidemiology of medical errors: a review of the literature

Medical errors are one of the most important quality problems in health care today. The best insight into the incidences and characteristics of medical errors is through studies on adverse events (AEs) since a considerable fraction of AEs are results of errors and as such preventable. Even though prevention is where effort should be directed to, only a few studies report on the preventability of AEs. Our aim is to give an overview of the literature reporting on AEs and their preventability.

We systematically searched Medline and Embase for literature published between 1980 and June 2002. All articles reporting primary data on incidences of AEs and their preventability were included.

The 8 articles retrieved were divided into two categories. 1) Four large scale retrospective studies: They reported incidences of AEs between 2.9% and 16.6% of all hospitalizations that were judged as preventable in 48.0-69.6% and negligent in up to 32.3%. 2) Four prospective studies: The reported rates of AEs vary remarkably (0.0037-39.0%) because of different detection methods used, different definitions applied and different health care settings studied. One prospective observational study identified AEs in 39.0% of hospitalized patients with a preventability of 18.0%. Two other studies, using process oriented incidence reporting detected rather low rates of AEs (4.2-5.4%) which were preventable in up to 62.5%. One prospective study in the outpatient setting, using voluntary incidence reporting detected only about 3.7 events per 100,000 clinic visits of which a high fraction was judged to be preventable (83.0%).

Incidence, medical outcome and costs of AEs warrant this issue to be high on any countries health care agenda. The U.S., Australia and Britain have adopted this challenge by creating a centre for quality improvement and patient safety within the health service and by enacting new laws. But real improvement of patient safety will need a fundamental change in medicine from a culture of individual blame and guilt to a culture of learning, system thinking and executive responsibility.