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Outside the Lab Guidelines and recommendations, Profession, Quality assurance and quality control, Regulation and standards

Diagnostic Error: Common, Catastrophic, and Costly

Diagnostic error is the most common cause of iatrogenic harm in US medicine – too many patients are suffering from these avoidable failures. The Society to Improve Diagnosis in Medicine is dedicated to reducing the incidence of diagnostic error and, in partnership with the Coalition to Improve Diagnosis, aims to improve diagnostic outcomes for both patients and healthcare systems. Laboratory physicians and scientists can play a significant role in achieving this goal.

Every year, 12 million adult Americans in outpatient settings experience a diagnostic error (1), defined by the National Academy of Medicine as the “the failure to establish an accurate and timely explanation of the patient’s health problem(s) or communicate that explanation to the patient (2).” Approximately 100,000 patients lose their lives prematurely in hospitals alone (3). It is a complex problem and the causes are many, but the opportunity for laboratory physicians and scientists to play a greater role in solutions to this problem spurred me to leave my longstanding career in laboratory diagnostics to focus on the notion that laboratory medicine can make a greater difference to patient outcomes than it does now. In fact, it is a critical element of healthcare and can make or break a patient’s hopes for the future – particularly in the context of diagnostic error.

Patient and health system impact
When patients seek medical care, they trust their clinicians to make the right diagnosis. When failures happen, this trust is tested, the relationship between doctor and patient weakens, and patients are left feeling worried that they may not get well or find out what is wrong with them. We all know a family member or friend who has gone on diagnostic journeys that went on too long or produced wrong answers, sometimes with catastrophic outcomes.

Diagnostic error is the number one cause of preventable harm in our health system – some say larger than every other safety issue (e.g. medication errors, wrong-side surgery, hospital-acquired infections) combined. But the significance of diagnostic error impacts not just the patient, but also the health system – there are estimates that it costs the US economy in excess of US$100 billion per year (4). The domino effect of such an error is intuitive: if the diagnosis is wrong, how likely is it that the treatment plan is right?

Common causes

Coming up with an accurate diagnosis is a complex process.

The causes of missed or delayed diagnosis are many. With over 10,000 diseases, 4,000 tests (not including all genetic variants available for testing), and only 50-100 common symptoms, coming up with an accurate diagnosis is a complex process. And with all diagnoses, there is uncertainty. The disease process and its presentation evolve over the course of the illness, but presentations can also vary substantially between patients – only adding to the difficulty. With this level of uncertainty and variability, it can be hard to generalize about what constitutes a timely diagnosis. Egregious delays tend to be obvious in retrospect, but differentiating between inappropriate delay and conservative approaches to diagnosis can be daunting. In many ways, it’s amazing that clinicians do as well as they do with estimates of diagnostic accuracy and timeliness at approximately 90%. Still, some clinicians and some systems do better than others, so we know improvement is possible.  

The role of testing in diagnostic quality
If you examine malpractice claims leading to death or permanent disability, diagnostic errors form the largest category. Of these claims, approximately 75 percent fit into one of three categories: vascular events, infections, and cancers.While the average claim had more than three contributing factors, clinician judgment was involved in 85 percent of all serious diagnostic errors – often due to the failure to order the correct test or interpret the result properly (5).

Ordering the correct test has been made somewhat more difficult by the attention given to the overuse of tests and procedures in medicine. While unintentional, this focus has potentially led to a bias towards under-ordering rather than appropriateness. Yet, research has shown that under-ordering of appropriate tests is more prevalent than over-ordering (6). A focus on appropriateness could have a large positive impact on reducing diagnostic error. 

Another common cause of diagnostic error related to judgment is failure to create a proper differential diagnosis – that is, the establishment of the list of disorders that could fit the signs and symptoms (5). If the true disorder is not on the differential, then it is likely that the tests needed to confirm or rule it out won’t be ordered. Independent of the differential, we also know that clinicians are often uncertain about what tests to order or how to interpret the results (7).

In addition to clinical judgment issues, the research highlights communication and system issues. In fact, 33 percent of claims involve communication issues – some of which involve communicating test results to patients. System issues include failure or delay in processing tests, receiving results, or executing follow-up of test results (5).

What needs to be done
We owe it to patients to improve diagnosis and this will take addressing multiple structural and process gaps, because there is no one cause for this tragic problem. We need a standardized approach to identifying diagnostic errors when they occur, a quality system that collects diagnostic error data, processes to learn from the data, and the tools to do something about it.

Most diagnostic errors involve both cognitive and system failures.

Despite its prevalence, diagnostic error is rarely a top priority for healthcare quality. Most incident reporting systems do not have a category for these errors; instead, they are distributed across multiple other categories, concealing their cumulative burden. We also haven’t established consistent methods to study them effectively. For example, if an adverse event involves clinician judgment, it is typically sent to peer review; if system failures are identified, it goes to root-cause analysis. But we know that most diagnostic errors involve both cognitive and system failures, thus this bifurcated approach fails to holistically analyze causes which could lead to more impactful findings.  

The clinical laboratory has a major opportunity to contribute to resolving this problem. While the laboratory itself is one of the highest quality and most reliable settings in the health system, the pre- and post-analytical phases that include test ordering and result interpretation are major opportunities for improvement – and laboratory physicians and scientists are uniquely positioned to provide leadership in this area. Recognizing this need, many laboratory professional organizations have joined with the Society to Improve Diagnosis in Medicine (SIDM) and participate in its Coalition to Improve Diagnosis

SIDM and the Coalition to Improve Diagnosis
At SIDM’s strategic planning meeting in 2013, we discussed the lack of awareness of the problem and the dearth of research to understand and improve it. We petitioned the National Academy of Medicine (NAM, formerly the Institute of Medicine) to study the problem, which they agreed to do.   Expecting the results in 2015, and concerned that the report might not drive action without purposeful next steps, SIDM convened the Coalition to Improve Diagnosis.

The Coalition formed in August 2015 with 14 members, one month prior to the publication of the NAM report – and we have been growing ever since, numbering now more than sixty. Our membership is diverse and includes medical professional associations, accrediting organizations, health systems, and patient safety, disease-specific patient advocacy, and health management organizations. It also includes liaisons from multiple government agencies.

The objectives of the Coalition are threefold: subscribe to a common set of principles; work together on collective actions; and have member organizations commit to taking their own action directed toward improving diagnosis. The collective actions thus far have focused on: building awareness and engagement; advocating for increased research funding from Congress; and identifying and disseminating effective interventions.

The success story – so far
The group’s collective actions have already helped raise awareness of the challenges facing diagnostic medicine. In 2018, the coalition launched the ACT for Better Diagnosis campaign as a targeted effort to increase awareness of the need to improve Accuracy, Communication, and Timeliness. The group developed a consensus document calling for more congressional funding and, in 2019, Congress created a new line item with earmarked funding for diagnostic quality, along with the creation of an interagency taskforce to address a coordinated response. In 2020, an increase in the funding occurred.

Media coverage of diagnostic error has grown dramatically since our efforts began, which has helped significantly, and our members are making great progress in their individual actions. Several organizations have established major initiatives around this problem – some small, some large – which represent a tremendous effort that was non-existent before the coalition was formed.

Measuring future success
Going forward, a clear reduction in diagnostic errors will be the best evidence of the Coalition’s success. Even now, activities in the field are snowballing – from the National Quality Forum’s new study section (their second on diagnostic errors) to an increase in grant opportunities from government agencies and private foundations. 

It is a long process, but we will only get there by taking action now.

Significant progress takes time. Engaging a community of stakeholders to successfully run a multipronged initiative on the problem reflected by a marked decrease in errors will be a multi-year effort. Given that we still are absent rigorous measures to count diagnostic errors locally or nationally, seeing a numerical reduction in error in the next two to three years is unlikely. However, we can assemble an ever-growing body of anecdotal evidence about what works and slowly move towards consensus measures and improvement strategies. It is a long process, but we will only get there by taking action now.

At this moment, the Coalition is solely a US effort because so much of practice is driven by country-specific policies and payment systems. However, diagnostic error is a global problem and SIDM works with stakeholders in every country that is interested, convening educational meetings. We even recently established an affiliate chapter in Australia. Global problems need global efforts to find global solutions.

Based on SIDM’s research, we know that diagnostic errors are the most common, most catastrophic, and most costly of all medical errors. To make a significant difference, each of us needs to play a part to reduce these errors. In particular, laboratory physicians and scientists have a growing number of tools to increase objective evidence that supports diagnosis, but they are tools that need the professionals who wield them to ensure they are used properly. Together, we will reduce the devastating consequences for our patients and for the healthcare system.

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  1. H Singh et al., BMJ Qual Saf, 23, 727 (2014). PMID: 24742777.
  2. National Academies of Sciences, Engineering, and Medicine, Improving Diagnosis in Health Care. The National Academies Press: 2015. PMID: 26803862.
  3. CG Gunderson et al., BMJ Qual Saf, 29, 1008 (2020). PMID: 32269070.
  4. DE Newman-Toker, “The Team Sport of Diagnosis: A Culture Shift Can Reduce Missed Diagnoses” (2016). Available at:
  5. DE Newman-Toker et al., Diagnosis, 6, 227 (2019). PMID: 31535832.
  6. M Zhi et al., PLoS ONE, 8, e78962 (2013). PMID: 24260139. 
  7. J Hickner et al., J Am Board Family Med, 27, 268 (2014). PMID: 24610189.
About the Author
Paul Epner

Chief Executive Officer and Co-Founder of the Society to Improve Diagnosis in Medicine and Chair of the Coalition to Improve Diagnosis.

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