I have been in the medical world for over 30 years, most of them in the field of Medical Oncology. I try to remember some of the mistakes I have made throughout this time and one of them had a real influence in my search of improving diagnosis. This is the story…
Marcos was a 22-year-old man on summer holidays. When he was swimming at the beach a strong wave rolled over him hitting his neck against the sand. Five hours later he started to feel sick with mild fever and sore throat. He went to the Emergency Room(ER). After the examination and I only noticed a moderate leukocytosis in the blood test and mild pain in his neck. Since there were no other symptoms, I told him to go home with some advices about possible evolution.
Three hours later the patient returned to the hospital feeling very sick and showing petechiae throughout her body and neck stiffness, requiring an ICU admission. Fortunately the evolution was favorable and he returned home some days later without problems.
Six months earlier, also at the ER, I saw an old patient with a diagnosis of bacterial meningitis with fever, neck stiffness and altered consciousness. My way of thinking at the present was that because a diagnosis such as bacterial meningitis is so uncommon, the possibility of a new one in a short period of time was very low.
Diagnostic error: we could consider it as a “non-fault” error due to the lack of data for an initial diagnosis. But also some cognitive biases participated.
Overconfidence: due to the desire to expedite the emergency service, I decided to leave the patient, warning him to return if his condition worsened.
The fallacy of the player or Montecarlo fallacy: to think that the probability of a present event is influenced by an earlier event. In this case the fact of a diagnosis of meningitis six months earlier, raised in my brain a lower probability for the same thing to occur in the present.
Representation heuristic: Bacterial meningitis is uncommon in young adults and I had in my brain the typical representation of fever, neck stiffness and altered mental status, but in a recent paper (1) , neck stiffness was only found in 17 of 27 (63%) episodes of bacterial meningitis, in a prospective study.
(1) Khatib U, et al. Journal of Infection (2017) 74, 1e9.Adults with suspected central nervous system infection: A prospective study of diagnostic accuracy