Diagnostic error is recognized as a significant public health issue, affecting millions of patients annually. This type of error is not always the result of negligence but is often an inherent risk in medical decision-making, which takes place under conditions of uncertainty and time pressure.
Defining Diagnostic Error and Measuring Prevalence
A diagnostic error is broadly defined as a failure to establish an accurate and timely explanation of a patient’s health problem or to communicate that explanation effectively. This definition encompasses three distinct outcomes: a missed diagnosis (condition never identified), a wrong diagnosis (incorrect identification leading to inappropriate treatment), or a delayed diagnosis (correct but determined too late, allowing the condition to worsen).
Measuring the true prevalence of diagnostic errors is challenging due to a lack of consistent reporting and the time gap between when an error occurs and when it is detected. Estimates rely on various data sources, including medical malpractice claims, autopsy studies, and retrospective reviews of electronic health records. Autopsy studies have historically shown major diagnostic discrepancies in 10% to 20% of cases.
In outpatient primary care settings, roughly 5% of adult patients experience a diagnostic error each year, translating to over 12 million Americans. While not all of these errors result in harm, a notable portion leads to serious consequences. Some studies suggest that preventable diagnostic errors lead to hundreds of thousands of serious harms, including death and permanent disability, each year in the United States.
Categories of Contributing Factors
Diagnostic errors stem from a combination of human factors and the characteristics of the healthcare system itself. These contributing factors are typically categorized into cognitive errors, which relate to the physician’s thinking process, and systemic errors, which involve institutional and process failures. Cognitive factors are often based on the use of mental shortcuts, known as heuristics, which can lead to biases in clinical judgment.
One common cognitive bias is anchoring, where a physician locks onto initial information and fails to adjust the diagnosis even when later data contradicts it. Confirmation bias occurs when a clinician selectively seeks out or interprets evidence that supports their initial hypothesis while ignoring information that might refute it. Another frequent pitfall is premature closure, where the diagnostic process stops prematurely once a plausible explanation is found, without considering other possibilities.
Systemic factors often contribute to diagnostic error, sometimes coexisting with cognitive failures. Institutional issues like fragmented care coordination, where patient information is not efficiently shared, create vulnerabilities. Time constraints and high workload pressures can force clinicians to rely on fast, intuitive thinking that is prone to cognitive errors. Problems with electronic health record usability and the failure to establish consistent protocols for following up on test results also represent significant systemic flaws.
High-Risk Medical Conditions and Care Settings
Research has consistently identified specific medical conditions that are disproportionately involved in misdiagnosis leading to serious patient harm. These conditions are often referred to as the “Big Three” error categories: vascular events, infections, and cancers. Together, these three groups account for nearly 75% of all serious injuries or deaths resulting from diagnostic errors. Within these categories, specific conditions like stroke, sepsis, and lung cancer are the most frequently implicated.
Vascular events, such as heart attack and aortic dissection, are often missed because their symptoms can be vague or mimic less serious conditions like heartburn or anxiety. Infections, including spinal abscess and meningitis, present diagnostic challenges because their early signs can resemble common viral illnesses. Cancers, particularly lung, breast, and colorectal, are frequently subjected to delayed diagnosis, often due to a failure to order appropriate screening or follow up on suspicious findings.
Diagnostic errors occur across all parts of the healthcare system, but certain settings pose a higher risk. Emergency departments (EDs) are high-risk environments due to the rapid pace, high complexity of cases, and the need for quick decisions under pressure. In the ED, serious misdiagnosis-related harms are estimated to affect a substantial number of patients each year. Outpatient primary care also sees a high volume of errors, and time constraints can limit the ability to gather a complete history or create a broad differential diagnosis.
Patient Strategies for Reducing Misdiagnosis Risk
Patients can take an active role in their healthcare to minimize the risk of a diagnostic error. Maintaining a personal health record is extremely helpful. Bringing a detailed, written list of all symptoms, including their onset, duration, and any alleviating or aggravating factors, ensures that no critical detail is overlooked during a consultation. This preparation allows for the most accurate information to be presented within the limited time of an appointment.
Patients should feel empowered to ask clarifying questions about the diagnosis and the reasoning behind it. Specifically, asking “What else could this be?” prompts the clinician to consider alternative diagnoses and helps to counteract the effects of premature closure. Furthermore, asking about the plan for follow-up—including what symptoms would warrant an immediate return—establishes a safety net for monitoring the course of the illness.
Seeking a second opinion is a valuable step, particularly for serious or life-altering diagnoses, or when symptoms persist despite treatment. Consulting another specialist provides a fresh perspective and can either confirm the initial diagnosis or highlight overlooked possibilities. Patients must also ensure continuity of care by confirming that all diagnostic tests, including lab work and imaging, are completed and that they receive and understand the results, rather than assuming that “no news is good news”.