Study Finds Outpatient Diagnostic Errors Affect 1 in 20 Adults

A new study co-funded by AHRQ found that diagnostic errors – missed opportunities to make a timely or correct diagnosis based on available evidence – occur in about 5 percent of U.S. adults and that about half of those errors could severely harm patients. The study and abstract of“The frequency of diagnostic errors in outpatient care: estimations from three large observational studies involving U.S. adult populations” was published online April 17 in BMJ Quality & Safety. The study used data from three previous studies of errors in general primary care diagnosis, colorectal cancer diagnosis and lung cancer diagnosis. In all three studies, diagnostic errors were confirmed through rigorous chart review. Diagnostic errors can harm patients by delaying their treatment. For example, a delayed or incorrect cancer diagnosis could make the disease harder to treat or more likely to be fatal. The study is significant because it is based on a large sample size and is the most robust estimate thus far to address the frequency of diagnostic error in routine outpatient care.

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2014 Apr 17. doi: 10.1136/bmjqs-2013-002627. [Epub ahead of print]

The frequency of diagnostic errors in outpatient care: estimations from three large observational studies involving US adult populations.

Singh H1, Meyer AN, Thomas EJ.

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Abstract

BACKGROUND:

The frequency of outpatient diagnostic errors is challenging to determine due to varying error definitions and the need to review data across multiple providers and care settings over time. We estimated the frequency of diagnostic errors in the US adult population by synthesising data from three previous studies of clinic-based populations that used conceptually similar definitions of diagnostic error.

METHODS:

Data sources included two previous studies that used electronic triggers, or algorithms, to detect unusual patterns of return visits after an initial primary care visit or lack of follow-up of abnormal clinical findings related to colorectal cancer, both suggestive of diagnostic errors. A third study examined consecutive cases of lung cancer. In all three studies, diagnostic errors were confirmed through chart review and defined as missed opportunities to make a timely or correct diagnosis based on available evidence. We extrapolated the frequency of diagnostic error obtained from our studies to the US adult population, using the primary care study to estimate rates of diagnostic error for acute conditions (and exacerbations of existing conditions) and the two cancer studies to conservatively estimate rates of missed diagnosis of colorectal and lung cancer (as proxies for other serious chronic conditions).

RESULTS:

Combining estimates from the three studies yielded a rate of outpatient diagnostic errors of 5.08%, or approximately 12 million US adults every year. Based upon previous work, we estimate that about half of these errors could potentially be harmful.

CONCLUSIONS:

Our population-based estimate suggests that diagnostic errors affect at least 1 in 20 US adults. This foundational evidence should encourage policymakers, healthcare organisations and researchers to start measuring and reducing diagnostic errors.