The Pursuit of Diagnostic Excellence.

A 1957 study of diagnostic errors starts with this sentence: “The cornerstone of internal medicine is correctness of diagnosis.”1(p108) This concept readily extends to most physician specialties. Without the correct diagnosis, our advice to patients will lack accuracy about treatment possibilities and prognosis. Because correct diagnosis has such importance, medical education should stress diagnostic excellence as a key goal. Brush and colleagues2 discuss one aspect of diagnostic excellence: probability revision. Medical students revise probabilities at a better rate than chance alone. Brush and colleagues found that students who received specific training on posttest probability revision performed slightly better on a paper task than those who learned about some disease manifestations, but all moved toward the correct posttest probability. Diagnostic reasoning is a dynamic, multidimensional activity of gathering and analyzing information. The data collection begins with a history and examination and often involves laboratory testing, imaging, and invasive testing. Unfortunately, errors in this process are prevalent. An Institute of Medicine report, “Improving Diagnosis in Health Care,”3 recognized diagnostic errors as a major cause of preventable patient harm.4 Many additional factors unrelated to an individual clinician’s diagnostic performance contribute to this issue, but the pursuit of diagnostic excellence is necessary for our patients’ benefit. The challenge becomes evident as one considers all the steps involved in making correct diagnoses. The process starts with taking the patient’s history, during which many diagnoses may become evident or substantial progress in narrowing our differential diagnosis is made. History taking is a more complex art than initially meets the eye, requiring broad knowledge of typical and atypical manifestations of a myriad of diseases. For example, when a patient has a chief concern of diarrhea, one must first characterize the bowel movements. Not all patients having diarrhea as a chief concern have stools that meet the technical definition of diarrhea. As we work to understand the patient’s presenting symptoms, their duration, and associated symptoms, we are (at least implicitly) matching the patient’s story with our illness scripts, akin to the processing that occurs when key words are entered into a search engine (eg, “best high intensity interval training class in DC”). As we ask questions, we are trying to develop a reasonable differential diagnosis for the patient’s symptoms. While we do not often assign numeric probabilities to this ever-changing list of possible causes, we repeatedly prioritize our differential diagnosis in the form of iterative hypothesis testing as new data are collected. Importantly, this process involves first the probability of a diagnosis but also considers the morbidity of potential diagnoses. That is, we consider a low-probability diagnosis because missing that diagnosis could have severe consequences. After taking the history, we look for physical findings that might help us refine our differential diagnosis. However, there are occasions in which history taking is delayed and/or guided by the initial inspection of the patient—sick vs not sick. For example, a patient with hypoxia gasping for air prioritizes stabilization over history taking. Depending on the history, we may focus more attention on certain aspects of the physical examination (ie, hypothesis-driven examination). Examining the patient can help us adjust our working differential diagnosis. Importantly, the diagnostic path is not a 1-way street; our examination sometimes will prompt further history. For example, 1 of us (R.M.C.) admitted a patient with chest pain. The initial differential diagnosis prioritized cardiovascular causes such as acute coronary syndrome and pulmonary embolism. The examination revealed right upper + Related article