The second major category involves failure or delays in obtaining the appropriate testing. An included example of a failure to order proper testing describes a case of a chronically anticoagulated patient admitted for a psoas hematoma following bone marrow biopsy. After a period of inpatient observation, anticoagulation was restarted. Subsequently, the patient developed increasing extremity pain and tachycardia. A CT angiogram was not ordered until the following morning, nor performed for several additional hours. Active extravasation of blood into the hematoma was identified, and the patient was referred to interventional radiology. The diagnostic error was therefore classified as relating to the delays associated with testing and its effect on subsequent definitive management.

The remaining scope of diagnostic errors includes a veritable cornucopia of illustrative morsels. An example of inadequate physical examination interpretation is provided by failing to elicit reflexes in a patient with weakness, leading to a delayed diagnosis of Guillain-Barré. An example of an error in history-taking is illustrated by a patient with fecal impaction and kidney injury whose excessive ingestion of magnesium citrate was missed, delaying identification of serum magnesium level of 10.2 mg/dL. A patient was admitted with abdominal pain following hysteroscopy, and the free air seen on CT was thought to be related to the procedure, rather than the ultimate diagnosis of small bowel perforation. Other examples included patients transferred between services whose failure to include complete handover information led to other delays in care.

Each of these examples and their classifications into Diagnostic Error Evaluation and Research frameworks helps safety researchers develop strategies to improve processes systematically contributing to diagnostic errors. Understanding of the domains of diagnostic errors allows for further exploration of the foundational causes of subtypes of error, with the ultimate hope of identifying acceptable interventions to mitigate such deficiencies.

Circling back to the estimates of diagnostic errors causing severe harm to hundreds of thousands in the United States annually, it remains reasonable to recognize these estimates are built on precarious scaffolding and extrapolation from the authors’ own prior work. The issues and flaws in their methods have been competently dissected elsewhere.^4,5 Rather than rehash the accuracy of these estimates, however, an alternative thought experiment involves taking these numbers at face value. This includes such estimates as the rate of diagnostic error for diseases such as “aortic aneurysm and dissection” between 21.0 and 51.7 percent. These rates of error are, at the least, consistent with the colloquial “standard of care” for dissection which has been to “miss the diagnosis” initially. Similarly elevated rates of error, and related harms, are associated with other serious vascular, infectious disease, and cancer-related diagnoses, as well.