Patient Safety Topics
Diagnostic Error

Healthcare facilities have at their disposal many strategies that could potentially reduce the diagnostic error rate. Implementing interventions that establish strong and reliable feedback loops between and among physicians regarding diagnostic accuracy is a key step in the error-reduction process. Ensuring that all steps in the diagnostic testing phase occur correctly and that all results are communicated back to ordering physicians and patients is critically important, as are methods to enhance the effectiveness of diagnostic decision making.

Key Data and Statistics

​Authority analysts reviewed 100 events related to diagnostic error reported between June 2004 and November 2009 in an effort to determine if there were system solutions to diagnostic error, or if diagnostic error was so intimately connected to physicians’ cognitive processing that system solutions were not tenable. These events were found by searching on terms such as delayed diagnosis, wrong diagnosis, missed diagnosis, misdiagnosed, failure to diagnose, failure to treat, and medical follow-up.

Sample Authority Event Reports with Possible Cognitive Errors ​ ​

Event Report

Potential Cognitive Processing Error1,2

Potential Failure(s)

Patient is an infant seen in the ED [emergency department] during high flu season after an episode of vomiting and period of apnea observed by family. Was discharged, but returned later. Family reported that the patient had another episode of apnea. Patient was evaluated and transferred to another facility for clinical impression of apnea and reflux.

Availability heuristic. The tendency to accept a diagnosis based upon recent or vividly recalled cases or events rather than on prevalence or probability.

Authority report stated missed diagnosis of apnea and reflux. Physician potentially attributed symptoms to common flu, due to availability. A more thorough physical examination may have led to the discovery of other symptoms indicative of apnea and reflux.

Patient seen in the ED on day one and day two for complaints of shortness of breath and chest pain. Diagnosed with an upper respiratory infection and sent home each time. Subsequently later admitted and died. Coroner preliminary report indicated PE [pulmonary embolus] as cause of death.

Anchoring heuristic. The tendency to fixate on first impressions or initial symptoms without considering causes that appear later or those that do not support the initial hypothesis or diagnosis.

Authority report stated missed diagnosis of PE. Physician may have anchored on diagnosis "upper respiratory infection." Once a physician anchors on a diagnosis, it is very difficult to introduce new differential diagnoses. Physician may not have considered alternate diagnoses on subsequent visits.

Patient seen in ED on day one with complaints of abdominal pain. Patient evaluated, treated, and discharged with diagnosis of UTI [urinary tract infection]. The next day, patient presented to another facility and was diagnosed with a ruptured appendix.

Premature closure. Acceptance of a diagnosis before it has been fully vetted by considering alternative diagnoses or searching for data that contradict the initial diagnosis.

Authority report stated missed diagnosis of appendicitis. Physician omitted tests that would have led to diagnosis of ruptured appendix. Physician may have failed to consider differential diagnoses during history and physical portion of examination.

Patient presented to the ED on day one with complaints of chest pain. Stress test done, results negative, and patient discharged. The next day, patient returned to the ED with chest pain and tachypnea, and the left leg was blue and mottled. Dopplers of lower extremities confirmed extensive DVT [deep-vein thrombosis].

Anchoring heuristic.

Premature closure. Representative heuristic. Mental matching to diagnose conditions with characteristic presentations. Predisposes to lack of a differential diagnosis.

Authority report stated missed diagnosis of DVT. Physician may have anchored on diagnosis "acute coronary syndrome" due to complaints of chest pain. Physician may have latched on to representative symptom of chest pain, failing to perform tests to rule out other potential diagnoses (i.e., differential diagnoses).

A young man came to the ED for fainting and syncope, including the inability to speak for a few seconds with lateralizing symptoms and staring. In the ED, lab work was done but no CT [computed tomography] scan was ordered. Patient was discharged home with diagnosis of syncope and dehydration secondary to stress, with instructions to follow up with primary care physician. Subsequently, the primary care physician admitted the patient directly into the hospital, where a CT scan was performed and a brain lesion diagnosed.

Premature closure.

Context errors. Occur when the diagnosing physician is biased by patient history, previous diagnosis, or other factors and the case is formulated in the wrong context.

Authority report stated missed diagnosis of brain lesion. Physician may have attributed symptoms to "stress" and evaluated patient in this context. Physician may have failed to rule out other less likely but more serious diagnoses. Physician may have formulated diagnosis in the context of a young man with admitted stress and stopped searching for other plausible diagnoses for symptoms.


  1. Scott IA. Errors in clinical reasoning: causes and remedial strategies. BMJ 2009 Jun 8;338:b1860.
  2. Groopman J. How doctors think. New York (NY): Houghton Mifflin Company; 2008.

Excerpted from: Diagnostic error in acute care. Pa Patient Saf Advis 2010 Sep [cited 2017 Jun 16].

Educational Tools

DEER Taxonomy Chart Audit Tool
This adapted audit tool may be used to classify where a failure occurred during the diagnostic process.

Diagnostic Error Measures Worksheet
This sample worksheet may be used for documenting facility-specific process and outcome measures involving physician misdiagnosis.

Patient Education Regarding Diagnostic Error
This sample handout is intended to help healthcare providers encourage patients to be active participants in each and every physician encounter.

Pennsylvania Diagnostic Error in Acute Care

This research poster illustrates common causes of diagnostic errors reported in Pennsylvania, select outcome and process measures to identify errors in individual facilities, and strategies to prevent these errors.

A Physician Checklist for Diagnosis

This pocket resource for physicians includes a general checklist designed to minimize diagnostic error.


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Advisory Articles


Safety Tips for Patients



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