What is an error?

In response to the high rate of preventable morbidities and mortalities in hospitals, patient safety and quality initiatives have focused on the study of adverse events and errors, and their interactions.

As per the World Health Organization guidelines, an “adverse event” (AE) is defined as “any deviation from usual medical care that causes an injury to the patient or poses a risk of harm”. In specific, an event may result in “prolonged hospital stay, disability at the time of discharge or death” and is caused by healthcare management rather than the underlying medical condition. Preventable AEs are the result of error; while non-preventable AEs may be due to an unavoidable reaction or side-effect of treatment that is outside the healthcare provider’s ability to mitigate. Adverse events pose an economic burden on the healthcare system due to the additional costs of readmission, re-operation, lengthened hospital stays, hospital staffing, and subsequent litigation.

“Errors” are what drive preventable AEs and can be defined as a mechanism of deviated task execution, or “the failure of a planned action to be completed as intended [error of execution] or the use of a wrong plan to achieve an aim [error of planning]” as reported by the Institute of Medicine. An error may be either a commission or omission of an action, and may be categorized as “consequential” or “inconsequential”; “active” or “latent”. Active errors are the unsafe acts committed by frontline healthcare providers, and can be identified in the form of slips, lapses, mistakes and procedural violations. Their effects are often consequential, recognized immediately, and directly affect patient care. Latent errors, contrarily, are underlying failures in the system that are often inconsequential and difficult to detect but create local conditions that can lead to AEs. Examples of latent errors include poor OR design, incorrect equipment installation, heavy workloads, inadequate supervision and hospital staffing. While latent errors rarely have a direct and immediate impact on patient care, a combination of both latent and active errors can result in serious adverse patient outcomes.

Potential AEs are identified as “near-misses”, which are events that could have harmed the patient but did not due to either chance or timely intervention. While near-misses do not result in patient harm, it is believed that they share the same underlying factors as adverse events that do affect the patient. According to patient safety sources, near misses occur 3-300 times more often than adverse events. In a multicenter UK study, it was shown that only 2% of incident reports (n=30,000) were associated with a major adverse event for the patient – the remainder of the incidents were either minor events or near-misses. Occurring more frequently than adverse events, near-misses provide a valuable source of data for the study of nature and underlying causes of events.