Studies have shown that about 5% of autopsies in hospitals in the United States reveal lethal diagnostic errors, accounting for 40,000 to 80,000 deaths annually that could have been averted with a correct diagnosis and prompt and appropriate treatment. Despite the significant impact of diagnostic errors, the problem has received relatively little attention in clinical research.

Analyzing Long-Term Malpractice Data

In BMJ Quality and Safety, my colleagues and I published a study that sought to characterize the consequences of diagnostic errors by analyzing closed, paid malpractice claims. We reviewed data from the National Practitioner Data Bank (NPDB), an electronic repository of payments made on behalf of physicians with medical liability settlements or judgments. The NPDB also includes adverse peer review actions against licenses, clinical privileges, and professional society memberships. Diagnostic errors were defined as missed, wrong, or delayed as disclosed by subsequent tests or findings.


After analyzing more than 350,000 medical malpractice payments over 25 years, the most common and costly involved diagnostic errors. About 29% of these medical malpractice payments resulted from diagnostic errors, which also accounted for the largest fraction of total payments. Another 27% were from treatment errors, and 24% were from surgery-related errors. Diagnostic errors cost $38 billion in malpractice claims payouts over the past 25 years, with an average per-claim payout of more than $380,000. About 93% of payments were made on behalf of allopathic and osteopathic physicians, as opposed to nurse practitioners or other healthcare providers.

Death was the most frequent outcome resulting from diagnostic errors, followed by significant permanent injury, major permanent injury, and minor permanent injury. Our study also showed that 76% of diagnostic error claims resulted in death or permanent disability. Diagnostic errors accounted for 37% of these serious outcomes in the claims dataset, far more than any other category of malpractice allegation, including mistakes relating to treatment (21%), surgery (16%), obstetrics (10%), medication (5%), and all others (10%). More diagnostic errors occurred in outpatient than inpatient settings, but inpatient errors were more likely to be deadly.

Significant Implications of Diagnostic Errors

Although malpractice claims represent only a subset of true errors, our results suggest that diagnostic errors are likely the most common, the most costly, and the most deadly type of medical error. The  public health burden of diagnostic errors could be twice as high—80,000 to 160,000—as what has been previously estimated based on hospital mortality data alone. Healthcare stakeholders should consider diagnostic safety a critical health policy issue and make major efforts to address it going forward.