Because influenza was prevalent in the community, and a myriad of patients with the virus were seen this particular week, the EP was assured that this young lady had the flu—until she returned the next day with a petechial rash and sepsis from bacterial meningitis. This case illustrates the influence of “availability bias” in decision making. Treating a myriad of patients with the same symptoms, some with positive influenza screens and others with negative screens, led the physician to believe that the correct diagnosis, influenza for this patient, was the most common, some might say logical, diagnosis, while discounting other, and more serious possibilities as improbable.
By referring to the disease process that comes to mind most easily, and basing a diagnosis on previous patient experiences with similar symptoms, availability bias confounded the ability to look deeper into other possible causes. A more thorough neck examination, and careful skin and neurological examinations, coupled with the knowledge of a negative rapid influenza test, might have provided enough information—or doubt—to change the physician’s frame of reference and initially establish the correct diagnosis.
“Availability Bias” Mitigating Strategy: Always take a moment to consider diagnoses other than the most common in the differential and prove why the common diagnosis is valid and why other diagnoses could not be the case. If unable to do so, go back and re-evaluate.
Case Scenario 2: It Is Not Always ‘What It Is’
The next patient, a woman in her late 20s, presented to the ED less than 48 hours after discharge from the trauma service at another hospital. She had been admitted after a motor vehicle accident that resulted in an isolated traumatic subarachnoid hemorrhage. After observation, with no surgical intervention, she was discharged in good condition and was able to resume her normal activities with supportive care for a persistent headache postinjury. However, the patient returned after 2 days to an ED closer to her home, because she felt “foggy” and more irritable than usual.
As is customary, this busy unit employs nursing preemptive (ie, standing) orders, and the patient was triaged and laboratory tests were drawn including a basic chemistry panel. Upon evaluation by the attending EP, a concern for re-bleed led to a request for a noncontrast computed tomography (CT) scan of the head, which was interpreted as stable with no new bleed. The case was discussed with the trauma service from the initial hospital and follow-up was arranged.
Prior to the follow-up appointment, the patient returned to the ED because of a further deterioration in mental status. A third head CT was taken and interpreted as stable; however, her serum sodium level was 114 mmol/L. This patient suffered from posttraumatic syndrome of inappropriate antidiuretic hormone secretion (SIADH), and a retrospective review of the laboratory values from the prior ED visit showed the sodium level to be abnormally low at 121 mmol/L.
This case is a good illustration of “anchoring bias,” in which the existing diagnosis of traumatic subarachnoid hemorrhage was maintained as the etiology of the patient’s symptoms, despite a new piece of significant information (ie, the low sodium level) that was not integrated into the differential of possible etiologies for continued deterioration of mental status.
“Anchoring Bias” Mitigating Strategy: Awareness of the power of a prior diagnosis or opinion to mislead is paramount; be sure to carefully review all available data and account for anything that does not lie within the range expected for your diagnosis whenever a patient returns to the ED.
Case Scenario 3: The Search for the Right Piece of the Puzzle
A merchant marine in his mid-40s had fever, jaundice, vomiting, and right upper-quadrant pain for 2 days. He had been airlifted off his ship in the mid-Atlantic Ocean because the medical crew on the ship was concerned that he had a life-threatening illness and they had no surgical facilities available to care for acute cholecystitis with ascending cholangitis.
This patient was otherwise healthy and had all current immunizations. Upon arrival in the ED, he was given intravenous (IV) fluids, antiemetics, and medication for pain control while the workup was underway. He was somnolent and critically ill-appearing. As he spoke only German, a Red Cross interpreter was engaged in an attempt to obtain further information, but the patient was unable to provide additional history. The physician was able to elicit the travel history of the ship by connecting the interpreter with a crewmember on board and learned that the ship was on a return voyage from Haiti, a country endemic with Plasmodium falciparum. It was further determined that this patient was not taking malaria prophylaxis; his blood smear turned out to be positive for the disease.