Diagnostic errors are estimated to occur 10 to 15% of the times with the highest error rates in general care cases where patients are diagnostically undifferentiated, such as emergency rooms, family medicine and internal medicine. The article in the New England Journal of Medicine looked at why so many errors are made. In focused visual specialties such as radiology and pathology, error rates are much lower at 2%. Smart doctors make dumb mistakes when they fail to recognize that they are thinking on an intuitive level rather than on analytical level. That is, even doctors fall victim to cognitive bias which leads them to incorrect diagnoses. For instance, in 55% of fatal cases of pulmonary embolus, the diagnosis was completely missed. The brain processes information on two levels: an intuitive (Type 1) level and an analytical (Type 2) level. Intuitive Type 1 thinking is largely reflexive and autonomous often happening in the blink of an eye. These intuitive thinking patterns (heuristics) are either hard-wired into our brain or acquired through repeated experience. Trusting ones intuition is generally correct but not always. Unless physicians recognize when they are susceptible to Intuitive Type 1 errors, the misdiagnosis rate will not decrease.
Analytical thinking takes more conscious effort and mental resources. It is conscious, deliberate and generally reliable unless external factors such as fatigue, cognitive overload or emotional disturbances are present. Many clinicians are simply unaware of these cognitive biases and how Intuitive Type 1 thinking can lead to errors. Others don't appreciate just how much intuition affects their decisions. Examples of biases that cause misdiagnosis are representative bias, recency bias, diagnosis momentum, anchoring, and search satisficing.
Physicians need to consciously decouple from their intuitive thinking mode and consciously engage their analytical thinking mode in order to avoid diagnostic errors. It takes mental effort to override the intuitive mode. There are some practical ways that a patient and physician can avoid cognitive bias errors. The physician needs to ask herself what other conditions could be causing these symptoms, rather than considering one cause, ruling that out and stopping the inquiry. And if the physician doesn't seem to be paying enough attention, the patient should ask: What is the worst possible medical condition that can cause these problems? If physicians can avoid falling victim to their intuitions, fewer diagnostic mistakes will be made.