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Active error (or active failure)—The terms active and latent as applied to errors were coined by James Reason. Active errors occur at the point of contact between a human and some aspect of a larger system (e.g., a human–machine interface). They are generally readily apparent (e.g., pushing an incorrect button, ignoring a warning light) and almost always involve someone at the frontline. Active failures are sometimes referred to as errors at the sharp end, figuratively referring to a scalpel. In other words, errors at the sharp end are noticed first because they are committed by the person closest to the patient. This person may literally be holding a scalpel (e.g., an orthopedist operating on the wrong leg) or figuratively be administering any kind of therapy (e.g., a nurse programming an intravenous pump) or performing any aspect of care. Latent errors (or latent conditions), in contrast, refer to less apparent failures of organization or design that contributed to the occurrence of errors or allowed them to cause harm to patients. To complete the metaphor, latent errors are those at the other end of the scalpel—the blunt end—referring to the many layers of the healthcare system that affect the person “holding” the scalpel.

Adverse drug event (ADE)—An adverse event (i.e., injury resulting from medical care) involving medication use.


  • Anaphylaxis to penicillin

  • Major hemorrhage from heparin

  • Aminoglycoside-induced renal failure

  • Agranulocytosis from chloramphenicol

As with the more general term adverse event, the occurrence of an ADE does not necessarily indicate an error or poor quality of care. ADEs that involve an element of error (of either omission or commission) are often referred to as preventable ADEs. Medication errors that reached the patient but by good fortune did not cause any harm are often called potential ADEs. For instance, a serious allergic reaction to penicillin in a patient with no prior such history is an ADE, but so is the same reaction in a patient who has a known allergy history but receives penicillin due to a prescribing oversight. The former occurrence would count as an adverse drug reaction or nonpreventable ADE, while the latter would represent a preventable ADE. If a patient with a documented serious penicillin allergy received a penicillin-like antibiotic but happened not to react to it, this event would be characterized as a potential ADE.

An ameliorable ADE is one in which the patient experienced harm from a medication that, while not completely preventable, could have been mitigated. For instance, a patient taking a cholesterol-lowering agent (statin) may develop muscle pains and eventually progress to a more serious condition called rhabdomyolysis. Failure to periodically check a blood test that assesses muscle damage or failure to recognize this possible diagnosis in a patient taking statins who subsequently develops rhabdomyolysis would make this event an ameliorable ADE: harm from medical care that could have been lessened with earlier, appropriate management. Again, the initial development of ...

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