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Diagnostic errors remain an underemphasised and understudied area of patient safety research. We briefly summarise the methods that have been used to conduct research on epidemiology, contributing factors and interventions related to diagnostic error and outline directions for future research. Research methods that have studied epidemiology of diagnostic error provide some estimate on diagnostic error rates. However, there appears to be a large variability in the reported rates due to the heterogeneity of definitions and study methods used. Thus, future methods should focus on obtaining more precise estimates in different settings of care. This would lay the foundation for measuring error rates over time to evaluate improvements. Research methods have studied contributing factors for diagnostic error in both naturalistic and experimental settings. Both approaches have revealed important and complementary information. Newer conceptual models from outside healthcare are needed to advance the depth and rigour of analysis of systems and cognitive insights of causes of error. While the literature has suggested many potentially fruitful interventions for reducing diagnostic errors, most have not been systematically evaluated and/or widely implemented in practice. Research is needed to study promising intervention areas such as enhanced patient involvement in diagnosis, improving diagnosis through the use of electronic tools and identification and reduction of specific diagnostic process ‘pitfalls’ (eg, failure to conduct appropriate diagnostic evaluation of a breast lump after a ‘normal’ mammogram). The last decade of research on diagnostic error has made promising steps and laid a foundation for more rigorous methods to advance the field.
Diagnosis is one of the most important tasks a physician performs and determines subsequent treatment and patient outcomes. Although most patients can expect to be diagnosed correctly, diagnostic errors are being increasingly demonstrated in the patient safety literature.1–5 Recent research shows that diagnostic errors can often lead to severe consequences and preventable morbidity and mortality.2 6 7 Despite an urgency to study and reduce diagnostic errors, for various reasons discussed in other articles in the supplement, they have remained an underemphasised and understudied area of patient safety research.8 9
Over the past 5 years, the annual Diagnostic Error in Medicine (DEM) conferences have highlighted emerging research in this area, which we summarise here. For the purposes of this paper, we classify current research in this field into three main topic areas: (1) epidemiology of diagnostic error (frequency, types, detection methods); (2) causes of diagnostic error (cognitive and system issues) and (3) error prevention strategies (development, implementation and evaluation of interventions). This paper briefly summarises the methods that have been used to conduct research in these three areas, then outlines future research needs to better understand and reduce diagnostic error in medicine.
Multiple research methods, largely retrospective, have been used to examine the epidemiology of diagnostic error (for an extensive overview on incidence, see Graber's article in this issue)10 Commonly used data sources include reports of malpractice claims,6 11 chart reviews of selected diagnoses or hospital admissions2 12 and autopsy reports.13 14 While these studies have given us a general appreciation of the burden of the problem, these estimates of incidence of the problem are far from precise or generalisable. Retrospective methods also introduce hindsight bias in judgments about error determination. Nevertheless, one advantage of retrospective methods is the potential availability of longitudinal data that spans the continuum of care of the patient (ie, outpatient visits, multiple subsequent hospital admissions, outcomes, etc). This allows researchers to retrospectively track the evolution of the diagnostic process over time and link it to diagnostic outcomes (ie, final diagnosis).2
Prospective methods have advantages such as reduced hindsight bias but used infrequently to study the epidemiology of diagnostic error. One example is the use of ‘standardised patients’ who present to providers in routine clinical settings without revealing their actual purpose.15 16 One study involved 23 rheumatologists who were visited by a standardised patient with known psoriatic arthritis. The diagnosis was missed or wrong in nine visits (39%). However, such methods are resource intensive. Other types of prospective methods involve presentation of hypothetical cases to assess physician cognitive error rates.17 18 However, these methods are mainly used to determine how varying circumstances or characteristics of physicians or patients influence error rates, and do not help determine incidence rates representative of a certain population.
Although previous studies have given us a general appreciation of the burden of diagnostic error, the estimated incidence rates of diagnostic errors vary greatly, from about 1% to as high as 55% in certain diseases or patient groups.1 This large variation can in part be explained by four factors:
Obtaining more precise rates of error is an enormous challenge, given the heterogeneous data and methodological and logistical challenges noted above. Nevertheless, such an undertaking is necessary to establish base rates in common settings of care (primary care, general medical hospitals, etc), to both attract needed attention to the urgency and magnitude of the problem as well as prioritise and evaluate intervention efforts. Such a project could have an important impact in ways similar to the IOM's landmark report on medical errors and patient safety,22 which propelled the field of patient safety forward. Suggestions for specific methodological and research approaches to advance this agenda include:
Because many aspects of the diagnostic process are not easily captured using current study methods, the causes of diagnostic error are difficult to identify. Ideally, the diagnostic process is studied prospectively in a real clinical setting, but this poses substantial practical difficulties (eg, ethical issues, time constraints, measuring clinician thought processes unobtrusively, observer bias). Consequently, most studies conducted in naturalistic settings have examined the causes of diagnostic error retrospectively (eg, through record review which sometimes is followed by interviews).2 20 21 25 These studies have revealed vulnerabilities in clinical workflow processes or organisational issues that contribute to error (eg, policies that are ambiguous about who is responsible for test results follow-up).26 They have also yielded illustrative patterns of cognitive failures or biases, (ie, errors in the reasoning process of the physician),19 as well as the complexity of interaction between system and provider factors.25 Prospective evaluations have been generally restricted to artificial settings (eg, case vignette studies)27 and offer a complementary cognitive perspective.
Prior studies have revealed that the diagnostic step of ‘information synthesis’ was particularly prone to error.1 4 19 20 Retrospective studies conducted in naturalistic settings can identify contributory factors and types of diagnostic breakdowns7; however, they are seldom able to reveal the root causes of diagnostic error due to limited information about causality. For instance, in reviewing an error case in which a diagnosis was missed despite the availability of laboratory results to support the diagnosis, it may be difficult or impossible to know whether the physician lacked the appropriate knowledge to arrive at a correct diagnosis, or was influenced by a cognitive bias, distraction or faulty heuristic, or simply did not have time or access to the result.18 28 29
Prospective studies in controlled settings could be potentially useful to examine causal relationships. Experimental designs, in particular, can isolate the effects of certain biases or the mechanisms underlying the reasoning process.18 30 However, the next step for any such line of research would be to better understand how problems detected in the laboratory translate into real-world behaviours and problems. A key will be enabling a ‘culture of safety’ that will permit clinicians to honestly reflect on errors they have been involved in, and examine and test ways they could be prevented in their daily work in the future.
A recent systematic review evaluated the effects of patient safety strategies that focused on diagnostic error and found that only few strategies had an effect in terms of diagnostic error reduction or reduction of patient harm.34 While this review identified over 100 studies that tested the effects of interventions on the diagnostic process, two other recent narrative reviews showed that there are a large number of interventions that have been developed to reduce diagnostic errors, but have not been yet tested for their effectiveness. Specifically, these reviews evaluated the existing literature on outcomes of system-related and cognitive interventions.35 36 System-related interventions are those that are focused on addressing organisational process errors, and vulnerabilities, whereas cognitive interventions focus on improving physicians’ perceptual and thought processes (eg, educational interventions, cognitive de-biasing strategies; see related papers in supplement). Whereas many of the suggested interventions were judged to have great potential, only few were actually tested and implemented in practice. This paucity of published outcome studies underscores the urgent need to not only conceptualise and develop interventions but to systematically evaluate their effectiveness.
In conclusion, research on diagnostic error, although still nascent, has evolved significantly as compared with the state of knowledge a decade ago. In this paper, we highlight areas where research methods could propel the field forward in promising directions related to epidemiology, contributory factors and interventions. The recently founded Society of Improving Diagnosis in Medicine and the annual Diagnostic Error in Medicine conferences are platforms to bring together a multidisciplinary group of people (including clinicians, patients, researchers and educators) to advance the research agenda. This agenda could also be integrated with research agendas of other organisations (eg, National Institutes of Health, specialty societies as well as national research agendas, eg, the UK's large research agenda on cancer). Furthermore, funding in this area should be stimulated to operationalise this research agenda. Using well coordinated, multidisciplinary approaches, and with appropriate research support, the foundation laid thus far can lead to future methodological advancement in the field and to reduction of diagnostic errors.
Contributors: All authors listed have contributed sufficiently to the project to be included as authors and approved of the final version.
Competing interests: Dr Singh is supported by an NIH K23 career development award (K23CA125585), the VA National Center of Patient Safety, Agency for Health Care Research and Quality (R18HS017820), and in part by the Houston VA HSR&D Center of Excellence (HFP90-020). These sources had no role in the preparation, review, or approval of the manuscript.
Provenance and peer review: Commissioned; externally peer reviewed.