Misdiagnoses All Too Common: 1 in 20 US Adult Patients

Diedtra Henderson

April 22, 2014

At least 1 in 20 US adults receiving outpatient care, or 12 million patients annually, are misdiagnosed, and half of these medical errors could be harmful, according to a population-based estimate.

The authors hope the study prompts systematic measurement and reduction of medical errors.

Hardeep Singh, MD, MPH, from the Houston Veterans Affairs Center for Innovations in Quality, Effectiveness and Safety, Michael E. DeBakey Veterans Affairs Medical Center, and the Section of Health Services Research, Department of Medicine, Baylor College of Medicine, Houston, Texas, and coauthors published their results online April 17 in BMJ Quality and Safety.

Because definitions of medical errors vary, Dr. Singh and colleagues synthesized 3 studies that used "conceptually similar" definitions. Two of the studies used electronic triggers to spot unexpected return visits by patients who had been seen by their primary care clinician or troubling lack of follow-up by patients whose clinical findings for colorectal cancer, such as documented hematochezia, should have served as "red flags." The third study they analyzed involved consecutive cases of lung cancer, with abnormal chest X-rays serving as a red flag. In all 3 studies, diagnostic errors were confirmed through chart review.

The estimated diagnostic error rate yielded in the primary care study was 5.06% compared with 0.007% for the colorectal cancer study and 0.013% for the lung cancer study.

"Combining estimates from the three studies yields a rate of outpatient diagnostic errors of 5.08%, or approximately 12 million US adults every year. Based on our previous work, we estimated that about one-half of errors would have the potential to lead to severe harm," Dr. Singh and coauthors write.

The authors note that the contribution of the cancer misdiagnoses to the overall estimate was small, but potent, because delayed cancer diagnoses are thought to be the "most harmful and costly types of diagnostic error in the outpatient setting," and can have a ripple effect on such issues as malpractice claims.

"[W]e estimate the frequency of diagnostic error to be at least 5% in US outpatient adults, a number that entails a substantial patient safety risk," the authors conclude. "This population-based estimate should provide a foundation for policymakers, healthcare organisations and researchers to strengthen efforts to measure and reduce diagnostic errors."

Financial support for the studies referenced in the article was provided by the National Institutes of Health, the Veterans Affairs National Center of Patient Safety, and the Agency for Healthcare Research and Quality. Two study authors disclosed receiving financial support from the Houston VA Center for Innovations in Quality, Effectiveness and Safety.

BMJ Qual Saf. Published online April 17, 2014. Abstract


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