Diagnostic error, defined as a failure to establish an accurate and timely explanation of a patient’s health problem, represents a substantial public health issue. Getting the correct diagnosis is the foundational step in all medical care, guiding subsequent treatment decisions. When this initial step is missed, delayed, or incorrect, the consequences can range from worsened health outcomes to permanent disability and death. The diagnostic process is complex, involving multiple steps, providers, and systems, which creates various points where errors can occur.
Measuring the Scope of Diagnostic Errors
Quantifying the exact rate of diagnostic error across all healthcare settings is difficult because there is no single national tracking system. Researchers often rely on aggregated data from medical record reviews, malpractice claims, and autopsy studies. A 2015 report by the National Academies of Sciences, Engineering, and Medicine (NAM) estimated that approximately 5% of adults in the United States who seek outpatient care each year experience a diagnostic error. This translates to more than 12 million adults annually. Recent studies suggest that diagnostic errors may affect nearly 795,000 Americans each year, resulting in death or permanent disability. The overall rate of diagnostic inaccuracy in medicine is frequently cited to be between 10% and 15%.
Diagnostic failures are categorized into three types:
- A misdiagnosis occurs when the patient is identified with the wrong illness, often leading to inappropriate treatment.
- A delayed diagnosis is made when the correct condition is identified only after an avoidable passage of time, allowing the disease to progress.
- A missed diagnosis is the complete failure to recognize that a serious condition exists.
Primary Factors Contributing to Error
Diagnostic errors stem from a combination of human cognitive factors and systemic failures. The human element involves mental shortcuts, known as heuristics, that doctors use to quickly process complex information, which can lead to predictable errors in judgment.
Cognitive Biases
One such error is anchoring bias, where a clinician locks onto an initial impression and fails to adjust the diagnosis when new evidence contradicts it. Premature closure is the act of stopping the diagnostic investigation once a plausible diagnosis is reached, without fully considering other possibilities. Availability bias occurs when a clinician overestimates the probability of a disease because they have recently seen a case or because it is a memorable condition. These biases are often unconscious and are not indicators of a lack of medical knowledge but rather a function of how the human brain processes information under pressure.
Systemic Failures
System failures, independent of the individual clinician’s thought process, contribute to a majority of diagnostic errors. Inadequate communication between specialists or departments frequently causes breakdowns in the diagnostic process. Fragmentation of patient medical records, particularly when care is received across multiple health systems, can lead to missing information necessary for an accurate diagnosis. Furthermore, the lack of reliable systems for tracking and following up on ordered diagnostic tests is a significant factor. When abnormal test results are not reviewed or communicated in a timely manner, a delayed or missed diagnosis can occur. Time pressures in clinical settings, especially during short appointments, also limit the opportunity for comprehensive history-taking and thorough physical examination.
Conditions Most Frequently Misdiagnosed
Certain diseases are disproportionately responsible for the most serious harm resulting from diagnostic errors. The “Big Three”—vascular events, infections, and cancers—account for nearly three-quarters of all serious misdiagnosis-related injuries. These conditions are difficult to diagnose because their early symptoms often overlap with more common, less serious illnesses.
Vascular events, such as stroke, heart attack (myocardial infarction), and blood clots, are frequently misidentified in their early stages. Stroke is a leading cause of serious harm from misdiagnosis, often mistaken for conditions like vertigo or migraines. The consequences of this delay are severe, as time-sensitive treatments are only effective within a narrow window.
High-stakes infections, including sepsis, meningitis, and spinal infections, are also commonly missed or delayed. Sepsis, a life-threatening response to infection, can escalate rapidly, yet its early signs may be dismissed as a simple viral illness or flu. A timely diagnosis is paramount, as delayed antibiotic treatment can quickly lead to organ failure and death.
Cancers, particularly lung, breast, and colorectal, are responsible for a large percentage of diagnostic errors because their initial symptoms are vague. A persistent cough may be treated as bronchitis while masking an underlying lung malignancy. Abdominal pain or changes in bowel habits may be incorrectly attributed to a benign condition like irritable bowel syndrome (IBS), allowing the cancer to progress.
The Patient’s Role in Minimizing Risk
Patients can take an active role in the diagnostic process to help mitigate the risk of error. Maintaining a detailed personal health record, including a concise timeline of symptoms, past medical history, and current medications, is a constructive action. Presenting an organized, written symptom history ensures that no pertinent details are omitted during a time-limited appointment.
During the visit, patients should ask clarifying questions about the diagnostic plan. A simple but effective question to pose is, “What else could this be?” which encourages the provider to consider the differential diagnosis and articulate their reasoning. It is also helpful to ask about the next steps and the expected timeline for receiving and reviewing test results, ensuring a closed-loop system for follow-up.
Patients should feel comfortable seeking a second opinion, especially when symptoms persist, the diagnosis is uncertain, or the proposed treatment is not yielding expected results. Engaging with the healthcare team as a knowledgeable partner strengthens communication and provides an additional layer of safety in the diagnostic journey.