Medical error
Medical error refers to the failure of a planned clinical action to be completed as intended or the use of an incorrect plan to achieve a therapeutic goal, encompassing acts of commission or omission by healthcare providers that result in preventable harm to patients.[1][2] Common categories include diagnostic inaccuracies, medication dosing or administration mistakes, surgical mishaps, and procedural oversights, with medication errors often predominant across inpatient and outpatient settings.[1][3] These errors arise from systemic factors such as workload pressures, communication breakdowns, and inadequate protocols, rather than solely individual negligence, though human factors like fatigue contribute causally.[1][4] In the United States, medical errors are estimated to cause over 250,000 deaths annually, positioning them as a leading contributor to mortality, though this figure derives from extrapolations of adverse event reviews and faces scrutiny for potential overattribution, as not all hospital deaths involve causal errors and official vital statistics do not separately code iatrogenic harm.[1][5] Globally, preventable patient harm affects approximately 6% of medical encounters, with higher rates in resource-limited environments, underscoring errors as a pervasive public health challenge despite safety interventions like checklists and electronic records.[6] Controversies persist over underreporting—due to punitive cultures inhibiting disclosure—and varying definitions, which inflate or deflate estimates; for instance, broad inclusions of comorbidities as "errors" contrast with stricter causal analyses showing lower direct lethality.[5][7] Efforts to mitigate include mandatory reporting systems and root-cause analyses, yet persistent gaps highlight the need for causal reforms targeting high-risk processes like polypharmacy and transitions of care.[4][1]Definitions
Core Definitions and Classifications
A medical error is the failure of a planned action to be completed as intended (an error of execution) or the use of a wrong plan to achieve an aim (an error of planning).[1] This definition, drawn from cognitive psychology and adapted by the Institute of Medicine in its 2000 report To Err Is Human, emphasizes deviations from intended processes rather than outcomes alone.[1] Errors occur across healthcare delivery stages, including diagnosis, treatment, and prevention, and may involve acts of commission (performing an incorrect action) or omission (failing to perform a necessary action).[8] Unlike unavoidable complications from disease progression, medical errors stem from modifiable human or systemic factors.[9] Medical errors are classified by their nature, drawing from James Reason's error typology, into slips (action-based failures, such as administering the wrong dose due to distraction), lapses (memory-based omissions, like forgetting to order a test), mistakes (rule- or knowledge-based planning errors, such as selecting an inappropriate treatment protocol), and violations (intentional deviations from standards, though rare in non-malicious contexts).[10] By domain of practice, errors include diagnostic errors (e.g., missed or delayed diagnoses, affecting up to 10-15% of cases in acute settings per some estimates), therapeutic errors (e.g., medication dosing mistakes, comprising 20-30% of hospital errors), and preventive errors (e.g., failure to administer prophylaxis against venous thromboembolism).[9] [11] Severity-based classifications, such as the National Coordinating Council for Medication Error Reporting and Prevention (NCC MERP) index, categorize errors from Category A (no error, potential for harm) to Category I (error causing death), focusing on outcomes for medication-specific incidents but applicable more broadly to track preventability and impact.[12] Active errors, directly attributable to individuals at the point of care (e.g., a surgeon's procedural misstep), contrast with latent errors arising from upstream systemic weaknesses (e.g., inadequate staffing or faulty equipment design), highlighting the interplay between human factors and organizational conditions.[1] These frameworks aid in root-cause analysis, prioritizing interventions on high-frequency or high-consequence categories like medication and surgical errors, which account for substantial portions of reported incidents.[13]Distinctions from Adverse Events and Negligence
Medical error refers to the failure of a planned action to be completed as intended (execution error) or the use of a wrong plan to achieve an aim (planning error), which may or may not result in patient harm.[14][1] In contrast, an adverse event is defined as an unintended injury or complication caused by medical management rather than by the patient's underlying disease process, encompassing both preventable and non-preventable outcomes such as known side effects of treatment.[14][15] Not all medical errors lead to adverse events; for instance, a dosage miscalculation detected before administration constitutes an error but avoids harm, often termed a "near miss."[14] Conversely, some adverse events occur without error, arising from inherent risks of procedures like anesthesia complications that align with accepted standards despite causing harm.[1] Negligence, a legal concept, involves a breach of the duty of care owed to the patient, where the healthcare provider's actions fall below the standard expected of a reasonably competent professional in similar circumstances, proximately causing injury.[14][16] This distinguishes it from medical error, as not every error equates to negligence; an error may occur despite adherence to prevailing standards, such as an unpredictable diagnostic oversight in a complex case.[1] Studies indicate that only a fraction of adverse events—estimated at around 28% in the 1991 Harvard Medical Practice Study—involve negligence, highlighting that most errors stem from systemic factors rather than individual culpability meeting legal thresholds.[6] Negligent adverse events thus represent a subset where substandard care directly contributes to harm, subjecting providers to potential malpractice liability, whereas non-negligent errors focus on process improvements without implying fault.[14][16] These distinctions underscore a causal chain: errors can precipitate preventable adverse events, a portion of which may qualify as negligent if they deviate from professional norms.[1] Empirical analyses, such as those from the Institute of Medicine's 1999 report, emphasize that conflating these terms risks misdirecting interventions toward blame rather than error-proofing systems, as negligence requires proving foreseeability and breach, unlike the broader scope of errors amenable to quality controls.[14] Peer-reviewed reviews confirm that while errors are ubiquitous in high-complexity environments, adverse events often involve multifactorial contributors beyond single acts, and negligence claims succeed in fewer than 1 in 7 cases of identifiable errors leading to harm.[16]Prevalence and Impact
Key Statistical Estimates
The Institute of Medicine's 1999 report estimated 44,000 to 98,000 annual preventable deaths from medical errors in U.S. hospitals, based on extrapolations from regional studies like the Harvard Medical Practice Study and Utah-Colorado study, which identified adverse event rates of 2.9% to 3.7% in hospitalized patients.[17] A 2016 analysis in the BMJ estimated over 251,000 annual U.S. hospital deaths attributable to medical errors, deriving this from applying a 9.5% preventable adverse event rate to total hospital deaths.[18] More recent estimates focus on subsets like diagnostic errors, with a 2024 BMJ Quality & Safety study projecting 795,000 annual U.S. cases of permanent disability or death from misdiagnosis across care settings, based on prevalence data from primary care (11.1%), emergency departments (5.7%-15%), and inpatient settings (up to 23.5% for harmful errors).[19] For medication errors, a 2020 BMC Medicine review estimated that one in 30 patients experiences preventable harm globally, with U.S. figures aligning at similar rates when adjusted for inpatient and outpatient data.[20] Globally, the World Health Organization reported in 2023 that unsafe care causes over 3 million deaths annually, with patient harm affecting 1 in 10 hospitalized individuals and contributing to 134 million adverse events yearly.[21] A 2023 Imperial College London analysis estimated 6% prevalence of preventable harm across care settings, equating to roughly 1 in 20 patients worldwide.[22] Medication-related costs from errors were pegged at $42 billion USD annually by WHO initiatives.[23]| Estimate Type | Source | Key Figure | Scope |
|---|---|---|---|
| U.S. Preventable Hospital Deaths | IOM (1999) | 44,000–98,000/year | Hospitals |
| U.S. Total Medical Error Deaths | BMJ (2016) | >251,000/year | Hospitals |
| U.S. Diagnostic Error Harms | BMJ Quality & Safety (2024) | 795,000 disabilities/deaths/year | All settings |
| Global Unsafe Care Deaths | WHO (2023) | >3 million/year | All settings |
| Global Preventable Harm Prevalence | Imperial College (2023) | 6% (1 in 20 patients) | All settings |