Misdiagnoses cost the U.S. 800,000 deaths and serious disabilities every year, study finds

“Analyzing the nature of misdiagnoses also provides significant opportunities for solutions: The errors are many, but they are quite concentrated. According to the study, 15 diseases account for about half the misdiagnoses, and five diseases alone — stroke, sepsis, pneumonia, venous thromboembolism, and lung cancer — caused 300,000 serious harms, or almost 40% of the total, because clinicians failed to identify them in patients. “That’s a lot that you could accomplish if you cut those harms by 50% for just those five diseases — that would be 150,000 prevented serious permanent disabilities or death,” said [lead author of the BMJ Quality and Safety paper (estimating that 371,000 people die every year after a misdiagnosis and 424,000 are permanently disabled) and a professor of neurology at Johns Hopkins School of Medicine and director of its Center for Diagnostic Excellence David] Newman-Toker.

The overwhelming reason for misdiagnosis is cognitive error on part of the doctor, he said. Doctors may make poor diagnostic decisions because the signs of the disease aren’t typical, or because the symptoms are too common and not frequently associated with a severe disease: Dizziness, for instance, occurs in a majority of cases of stroke, but only very few cases of dizziness result in stroke.

Or, it may be an issue of bias, either circumstantial — for instance, overlooking the possibility that a young patient may be having a stroke, because it’s exceedingly rare — or systemic, resulting for instance in dismissal of symptoms reported by Black patients. (Newman-Toker said his research estimates that being a woman or a person of color increases chances of misdiagnoses by 20% to 30%.)

This means that finding a way to avoid such cognitive errors, at least in the most commonly misdiagnosed severe diseases, would save a large number of lives. A quick way to do it? Routinely incorporating a second opinion in visits, suggested Newman-Toker. “I believe that the quickest way to solve the diagnostic error problem in the real world would be to construct approaches that basically rely on the ‘phone a friend’ model,” he said. This doesn’t mean that the patient should have to seek a second opinion, but rather that providers should make it standard practice to consult with a colleague before providing a diagnosis or dismissing a patient.”

Full article, A Merelli, STAT, 2023.7.21

From the Discussion section of the BMJ Quality and Safety article: “Our results suggest that diagnostic error is probably the single largest source of deaths across all care settings (~371 000) linked to medical error. This number may exceed estimated deaths from all other patient safety concerns combined, regardless of which prior estimate of total deaths due to medical error (range 12 500–250 000) is considered. This seems plausible because prior estimates systematically undercount diagnostic errors and diagnostic errors more often cause serious harms than other errors.

[..] For some of the most harmful diseases in our list, correct initial diagnosis has been associated with substantial reductions in morbidity or mortality (eg, ischaemic stroke (~fivefold), aneurysmal subarachnoid haemorrhage (~fivefold), ruptured abdominal aortic aneurysm (~twofold)). Finally, large variation in diagnostic error and harm rates across demographic groups, diseases, clinical settings and individual institutions point to strong prospects of preventability for at least some harms.

Although the study estimated total diagnostic errors (2.59 M), this reflects only errors in patients with dangerous diseases, not all diagnostic errors. Total annual diagnostic errors in the USA likely number in the tens of millions, but the total is likely highly contingent on the threshold for defining a diagnostic error. This is different, however, than serious harms (death and permanent disability), which are more objectively defined, so less subject to this particular type of methodological heterogeneity.

The large absolute numbers of patients harmed should not be mistaken for an inordinately high per-incident case or per-visit risk. According to these results, a patient with a life-threatening or limb-threatening disease has a ~11% chance of being missed; because of the substantial risk of harm when a dangerous disease is missed, that same patient also has a ~4% overall chance of dying or becoming permanently disabled pursuant to a misdiagnosis. Admittedly, both are higher than what medical experts generally think of as an ‘acceptable’ miss rate for dangerous diseases (eg, <0.5%–1%). However, given over 1 billion healthcare visits per year in the USA, a patient visiting a doctor for any reason (ie, who may or may not have a dangerous underlying disease) likely has a <0.1% chance of suffering serious misdiagnosis-related harms. Thus, patients should not panic or lose faith in the healthcare system. [..]

Disease distributions for serious misdiagnosis-related harms differ across clinical settings and age groups. Missed vascular events and infections dominate in hospitals and emergency departments, while missed cancers likely dominate in primary care. In adult care, vascular events are typical, while in paediatric care, infections are typical. Thus, diseases that should be the focus of interventions to improve diagnostic performance would ideally be tailored to the specific clinical context.

This study focused on missed diagnoses (false negatives) of dangerous diseases. While it is desirable to prevent false negatives, practical realities may constrain our ability to do so. Implications for improving diagnosis must consider these results in the broader diagnostic context which includes overuse of diagnostic tests, false positive (mis-)diagnoses, incidental findings and overdiagnosis, because these are also associated with substantial harms and increased healthcare costs. Reducing missed diagnoses by increasing sensitivity at the expense of specificity (ie, trading false negatives for false positives by shifting clinical decision thresholds around ordering tests or interpreting test results) should not be considered ‘improving diagnosis’. Instead, diagnostic innovations that increase both sensitivity and specificity at a given test threshold are needed, as recently shown in a pilot tele-consult programme for dizziness and stroke in the emergency department. Economic modelling may be an important means to estimate the full future impact of solutions designed to improve diagnosis, before they are implemented.”