I read the May 2019 BCMJ editorial, “Mistaken,” with great sympathy for DRR. My stomach gave a lurch as I recalled hereto-suppressed memories of some of my mistakes from my practising past.
Literature exists on the consequences of believing that what we have been doing for some time without an incident is safe and good. As an example, after seeing six persons in a row who have the flu, we may conclude that the seventh person with vaguely similar symptoms does too, and that person may end up with the wrong diagnosis. We call this confirmation bias, a type of cognitive bias that involves favoring information that confirms your previously existing beliefs.
Diagnosis is a categorization and risk evaluation exercise. It combines historical, observational, physical, and investigational data with what we have learned, memorized, seen, or experienced. In practical terms, we may immediately think of a list of all possible scenarios, from worst to benign, or we may work out a differential diagnosis—the reasoned and weighted list of somewhat overlapping possibilities. We learn much of this in a sophisticated apprenticeship type of education over many years and we reinforce it with practise.
There are three problems with our approach. First, much of our medical practise takes place in a closed room without external confirmation of being up to date. Second, we work under pressure, the stress of time, and related exhaustion. Third, we tend to rely and respond to what is in front of us: spotting dangers in ill health. We are not trained to spot our own assumptions, which may be false. In our mind we carry biases, some of which are so startlingly obvious that they may be correctable (e.g., our perceptions related to our patients’ age, gender, race, or occupation). Other biases are more significant because they are less evident. We often do not challenge our immediate diagnostic response.
I clearly remember a 22-year-old new immigrant from Australia, an avid rugby player and outdoorsman, in the middle of the flu season, complaining of his cough. It wasn’t until 2 weeks later, when I ordered a chest X-ray, that I learned that he had advanced lung cancer. This was a long time ago, and I do not remember if I went through a worst-scenario list or a formal differential diagnosis procedure when I first examined him, but I do remember that he was a strong, well-presenting young man with his history of playing sports, and that lung cancer was not on my mind.
I am not sure how one teaches or how one learns to spot one’s assumptions—perhaps via mistakes. But we learn in medical school that mistakes are a no no! I admire our editor’s way of dealing with his mistake, and I am sure his story will help others. Also, when making a diagnosis, it might help to go through the process of thinking, “I may be wrong. I must consider the implications.”
—George Szasz, CM, MD
O’Sullivan ED, Schofield SJ. Cognitive bias in clinical medicine. J R Coll Physicians Edinb 2018;48:225-232.
This post has not been peer reviewed by the BCMJ Editorial Board.