Two common heuristics/biases that can sometimes lead to premature closure are the availability and anchoring biases. Availability bias means that the diagnoses easily thought of—and often most recent in the memory—are more likely to be assigned to a patient problem. The diagnosis of pulmonary embolism would be more “available” in a patient with fever, dyspnea, and normal CXR, especially if the clinician recently had seen a patient with PE. Anchoring bias occurs when early information is relied upon to make clinical judgments and the clinician fixates on a diagnosis despite acquiring additional or contrary information. For example, a clinician may rely upon a diagnosis of CAP based on the sign-out from a colleague, despite the one-month history of symptoms, rather than broadening the differential.
Clinician-focused methods to reduce diagnostic errors. Multiple methods exist that may mitigate diagnostic errors, although definitive proof of their value is still lacking, owing to the difficulty involved in studying such errors due to the multitude of causes.4 In our opinion, building a mental database of illness scripts by reading and seeing patients, as well as being metacognitive, are the best methods for individual clinicians to use to reduce their errors (see “deliberate practice” below).
Metacognition, or thinking about one’s thinking, is another method of reducing errors and can be characterized by “reflection in action” (reflection in real time) and “reflection on action” (reflection after an event).5 For example, taking a few moments at the end of a week on clinical service to reflect on the hospital course and diagnostic paths of the most complex patient presentations (reflection on action) is an exercise used to reduce errors.
For reflection in action, a clinician may pause when confronted with paradoxical findings for a current patient’s presentation (e.g. elevated jugular veinous pressure and crackles on exam but normal b-type natriuretic peptide), and “think aloud” (see below) to ensure he or she is processing all of the appropriate elements of the case.5
In the case presented above, the time course might have initiated reflection into erroneous decision-making at the moment the clinician thought that CAP was a possibility (reflection in action). Although direct evidence is inconclusive as to whether these techniques improve diagnostic accuracy, engaging in metacognitive exercises remains a cornerstone of seasoned clinical reasoning experts.6
Teaching and Learning Principles
Making a commitment. During a patient presentation, it is often helpful to ask a learner to develop a two- to four-item prioritized differential diagnosis list based on likelihood and/or lethality. Have the learner describe which diagnosis is most likely (i.e., the working diagnosis), in addition to the reasons “for” or “against” certain hypotheses. Once the diagnosis has been determined, combine commitment with an exercise in metacognition by asking the learner, “Why do you think that your initial diagnosis of Q-fever was incorrect?” Clinical educators may then follow up with teaching pearls and their approach to this type of case (see Table 1).
Think aloud: In this method, an instructor expresses his or her thoughts aloud in real time.7 By modeling this technique, attending physicians allow learners to observe the process of developing a differential diagnosis and plan. For example, during the admission process, instructors could verbalize their approach to fever in a systematic fashion (see Table 1) after the trainee has completed the presentation: “At this point I am considering an infectious cause such as pneumonia, given the respiratory symptoms, although the one-month history of fever and malaise makes me think that I should keep neoplasm and an unusual infection on my list of possibilities.”
Conversely, instructors can ask trainees to voice their thoughts aloud to better understand their reasoning processes. By using this method, instructors can also support, correct, or reinforce the trainees’ appropriate use of knowledge in the clinical reasoning process.