The early attention on improvement for diagnosis responded to cases of harm and thus focused on the negative, trying to define exactly what constituted an error. Investigators attempted to create a meaningful taxonomy clarifying what was lacking or wrong. Variations and subclassifications of the concept of diagnostic error followed from those efforts. Such efforts were often met with controversy as experts grappled with problems finding sufficient specificity and precision to be useful. Foundational terminology for diagnosis relating to suboptimal processes and outcomes are listed and defined below.
Diagnostic Error
The 2015 National Academy report sought a consensus definition for diagnostic error that is now adopted as an authoritative definition to guide the field.3 That definition embraces provider, health organization, and patient perspectives:
Diagnostic error is the failure to (a) establish an accurate and timely explanation of the patient’s health problem(s) or (b) communicate that explanation to the patient.
This definition was met with concern by some, who noted that “accurate” and “timely” are not standardized or specified, and judgments about what constitutes adequacy are still left to sometimes subjective or, at best, unclear standards.
The concept of error is particularly problematic for diagnosis as most diagnostic errors are real but generally not tangible (except for the harm they cause) or detectable until after the fact. The determination that a diagnostic error has occurred is subject to hindsight and outcome bias and is thus not entirely objective.29 In addition, diagnostic errors are difficult to measure, in part because many likely go unnoticed, and they may or may not be preventable or actionable.
The term “error” requires blame, even if circumstances are challenging and responsibility is diffuse. Analysis tends to focus on cognitive processes and system factors. Unlike safety “events,” diagnostic errors tend to become evident over time and across different sites and systems of care. Attribution to a single person, site, or moment may be difficult or even impossible. Descriptions of various categories of diagnostic error follow.
Diagnostic Failure
A failed process or a wrong or delayed diagnosis. Some refer to diagnostic process failures and diagnostic label failures, again emphasizing diagnosis as both a process and an outcome.5
Misdiagnosis
Use of a wrong diagnostic label. For example, a diagnosis of pneumothorax might be a wrong label (misdiagnosis) if the actual problem is a pleural bleb. Similar to the term wrong diagnosis or incorrect diagnosis.30
Missed Diagnosis
A condition that was present but was not identified or diagnosed. Since a diagnosis cannot be missed unless at some point it is recognized, the term implies that the diagnosis becomes known but is established late. The term is sometimes used when a diagnosis is first identified in post mortem examination but is sometimes used when a diagnosis is discovered after it has progressed to a point where potential for medical intervention is less than optimal. Thus, this term overlaps with the concept of delayed diagnosis.
Delayed Diagnosis
A diagnosis may be considered delayed if the time to diagnosis allows the condition to persist and worsen such that it impacts the potential to benefit from optimal management. It also is used if the time that elapses before diagnosis worsens prognosis or outcome or causes protracted processes that create inconvenience, burden, or excess cost.
From the patient perspective, delays in diagnosis can add to mental distress by prolonging uncertainty. Criteria for delayed versus timely diagnosis vary by condition, patient, and setting and are influenced by acuity and urgency for action. Again, criteria for timeliness are defined for some but not all conditions and likely vary by site depending on resources and demand.
Missed Opportunities for Diagnosis
This term acknowledges that at some point it becomes clear that an opportunity existed in the past to have done something different to improve diagnostic outcome, so it is only knowable in hindsight.31,32 Missed opportunities may be identified in followup visits or revealed in feedback; individuals may uncover them incidentally. Reflective practice can use missed opportunities for continuous learning.
Formal methods to identify missed opportunities can be supported by systems that use diagnostic e-triggers33,34 (such as measurement of unplanned hospital admissions with a preceding index visit) set up to detect missed diagnoses. Triggers are particularly well suited to problems that are known to have common lapses in care, such as detection of diagnostic clues of cancer that should have had followup.35
Missed opportunities are a subset of diagnostic error that may or may not be preventable but are actionable by design. The detection of missed opportunities is best suited to the quality paradigm since it is typically proactive and objective. However, methods to identify and respond to missed opportunities are often limited in scope for types of conditions with specific and predefined actions.
Adverse Events, Diagnostic Adverse Events
Defined under the Safety Paradigm section above, adverse event refers to an event that results in unintended harm encountered during medical care.3 In general, medical adverse events tend to be (but are not always) errors of commission (e.g., wrong site surgery). Diagnostic adverse events commonly include errors of omission (e.g., failure to order or properly interpret a diagnostic test).
Diagnostic Discrepancies or Diagnostic Discordance
Disagreements in classification of disease, commonly used in clinical pathology.36,37 The term is also used when there are disagreements between diagnoses pre- and post-mortem38 or between different experts at different points in time (e.g., difference between admitting and discharge diagnoses).39,40
Near-Miss
Not all errors cause harm, although under different circumstances they might. The concept of “error without harm” or an error rescued before harm impacts a specific patient is referred to as a near-miss. A circumstance that is generally hazardous but is not related to a specific patient is a latent safety threat, or, if recognized, an unsafe condition. If someone intervenes to prevent harm, it is sometimes referred to as a good catch.11
Undesirable Diagnostic Events
Specific, measurable, and actionable clinical situations likely to denote the presence of diagnostic error; similar to triggers, situations for which ongoing and proactive monitoring, case review, and improvement activities are likely beneficial. Intended to apply to routine problems that may be remedied using available resources.41
Overdiagnosis
Excessive testing or pursuit of diagnostic possibilities that does not improve patient outcome or reduce risk.42 In some cases, diagnostic activity may add risk from unnecessary medical intervention or add excessive or unnecessary cost, inconvenience, or anxiety. Since diagnostic activity takes place before certainty is reached, determinations about what is adequate, optimal, or excessive are subject to judgment and risk tolerance (of both the provider and the patient). Thus, criteria for overdiagnosis may be debated.
Foundational Terminology To Describe Parameters of Diagnostic Quality and Excellence
In contrast to classifications of error, other terms are used to assess what is desired and good.6 The following descriptors characterize attributes of diagnostic quality and excellence.
Accurate: Correct, Precise
A diagnosis that is based on sound clinical reasoning and evidence. The degree of precision required can be argued depending on the evidence available at the time. For example, a symptom of chest pain could be refined to ischemic chest pain, which could be further specified as acute coronary syndrome. When specificity is required, the less precise term would be inadequate. When evidence is not yet established, the less precise term would be more accurate.
Safe
Care that is free of harm from medical intervention; care that minimizes consequences of the underlying condition and optimizes the outcome.
Timely
Ensuring diagnoses are made without unnecessary delays. Some might suggest that this term be defined by time by which an intervention must be made to achieve optimal outcomes. For example, it could mean time to thrombolytics for STEMI or time to resection or other treatment for certain cancers, when evidence exists for such a standard. A patient might define timely as a plan that reduces the period of uncertainty.
Effective (Often Encompassing Accuracy)
Using up-to-date evidence-based practices to achieve accurate diagnoses (as a process). Can also refer to how well the clinical reasoning and testing perform to rule in or rule out diagnostic possibilities.
Efficient
Optimizing diagnostic processes and procedures. A patient might suggest that efficiency refers to ease, such as coordination of appointments and tests to minimize visits or efforts to minimize cost of diagnostic workups. A healthcare system might define efficiency as economizing on the use of staff or other resources or as avoiding unnecessary tests and procedures. The goal of efficient diagnosis might conflict with necessary and safe if identification of an uncommon condition is delayed while ruling out other more common or more serious conditions.
Equitable
As applied to diagnostic processes, providing care that does not vary in quality because of personal characteristics such as sex, age, geographic location and income.15 Equitable could also mean achieving diagnostic excellence, even if individual patients require different resources in that process.
Patient Centered
Prioritizing the needs, values, and preferences of individuals in diagnostic care. This term can also refer to engaging the patient to optimize the information used in diagnostic reasoning.
These parameters used to describe and assess diagnosis include many shades of gray with varying levels of specificity and sometimes competing priorities. Considered together, they create a rich, nuanced tapestry that captures the complexity of diagnosis.
