Cognitive biases can lead to serious patient safety events

A patient arrives in the emergency department with the following comorbidities: renal failure, diabetes, obesity, and hypertension. The patient, whose chief complaint is chest pain, is reported to the triage unit with back pain—a secondary complaint—because the patient has been previously treated at the facility for back issues. In fact, the patient was seen earlier in the day for a cortisone shot.

Because of the preconceptions born from the patient’s recent medical history, the primary nurse skips performing an independent evaluation of the patient, who is found deceased a short time later.

What are cognitive biases?

This case study showcases several cognitive biases. More than 100 cognitive biases are believed to exist. They are flaws or distortions in judgment and decision making, which have become increasingly recognized as contributors to patient safety events, such as unintended retention of foreign objects, wrong site surgeries, delays in treatment, and patient falls.

According to a 2015 report from the National Academies of Sciences, Engineering, and Medicine, Improving Diagnosis in Health Care, diagnostic errors are associated with 6 percent to 17 percent of the adverse events that occur in hospitals, with 28 percent of diagnostic errors being attributed to cognitive bias.*

Examples of cognitive bias include the following:

  • Anchoring bias: Giving weight to and reliance on initial information or impressions
  • Ascertainment bias: Shaping decision making based on prior expectations
  • Availability bias: Judging the likelihood of a diagnosis based on the ease with which examples can be retrieved
  • Confirmation bias: Selectively noticing or seeking information that confirms an opinion or impression
  • Diagnostic momentum: After a label has been assigned, momentum builds, reducing the ability to consider alternatives
  • Framing effect: How information is presented or how a question is asked may affect future decisions
  • Search satisficing/premature closure: Cease looking for findings once a potential cause has been identified or accept a diagnosis before considering or verifying all information

Recognizing cognitive bias

Several factors can contribute to the presence of cognitive biases in medical decision making. Personal factors, such as fatigue or emotional state, may play a role, as may patient factors, such as presenting with many comorbidities or without a complete medical history. System factors also may play a role, with issues stemming from workflow designs, poor teamwork or communication, and insufficient time to gather and interpret information.

As evidenced in the case study described at the beginning of this column, it is important that health care organizations recognize cognitive biases and put systems into place to alleviate the problem.

The Joint Commission recently published a Quick Safety e-newsletter on cognitive biases, which identified several safety actions to mitigate the effects of cognitive bias, including the following:

  • Enhance knowledge and awareness of cognitive biases
  • Enhance professional reasoning, critical thinking, and decision-making skills
  • Enhance work system conditions and workflow designs that affect cognition
  • Promote an organizational culture that supports the decision-making process

For a more detailed explanation of the types of cognitive biases that exist, as well as more information on safety actions to alleviate these biases, read Quick Safety 28: Cognitive biases in health care.


The thoughts and opinions expressed in this column are solely those of Dr. Pellegrini and do not necessarily represent those of The Joint Commission or the American College of Surgeons.

*Balogh EP, Miller BT, Ball JR (eds). Improving Diagnosis in Health Care. Washington, DC: National Academies Press, 2015.

The Joint Commission. Cognitive biases in health care. Quick Safety 28. October 25, 2016. Available at: Accessed October 26, 2016.

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