Heuristic trap

Since starting third-year, I've noticed that sometimes I form preconceptions of what a patient's diagnosis will be before I have examined that patient or even gathered a full history. My preceptor picked up on this when he observed me interviewing a patient this afternoon, and he talked to me about it. He calls it the "heuristic trap." To avoid the heuristic trap is to think as a physician.

Later on in the afternoon, a patient came in complaining of a dry cough that she has had for 8 months. She was also taking a blood pressure medication that can cause a chronic dry cough. The heuristic trap would have been to think that this patient's cough was caused by that medication but fail to fully think of other possible causes.

Instead, I went into the interview armed with this information but pushed myself to think of other causes of her cough. My patient told me that she also gets heartburn everyday, that it's worse when she's bending over to clean the floors, and that it gets better when she eats food, drinks water, and puts milk in her coffee instead of drinking it black. Also, she always sleeps on her side but never on her back. She denied that her cough got worse with exercise or with cold air. This history is very suggestive of gastroesophageal reflux disease (GERD), which can cause a chronic cough due to inflammation of the esophagus.

On exam, her lung sounds were clear making a chronic lung infection and asthma less likely.

Now I could give a proper differential diagnosis and plan when presenting to my attending:

1. GERD - strongly suggested by history
2. Side effect from blood pressure medication
3. Asthma - less likely; not suggested by history, no wheezes on exam
4. Chronic lung infection - less likely; not suggested by history, normal lung exam

We decided to give her a diagnostic treatment of a proton pump inhibitor (which decreases stomach acidity) and follow up in 2 weeks to see if her cough symptoms have improved. If her cough does not resolve, we will consider measuring the pH level in her esophagus to rule out GERD; we would also consider switching her blood pressure medication to one that does not cause cough to rule that out as a possibility.


My mentor says that most physicians must constantly train their minds to avoid the heuristic trap, to think broadly about what might cause a particular set of symptoms. That is, after all, part of a doctor's job description. The third year medical student is at the beginning of that mental training.