A paper published in April found that about 12 million Americans, or 5% of adults in this country, are being misdiagnosed every year. This news exploded all over Twitter. Anxious reports from media outlets such as NBC News, CBS News, the Boston Globe, and others fanned the flames.
The paper involves a fair amount of extrapolation and estimation reminiscent of the "440,000 deaths per year caused by medical error" study from last year.
Data from the authors' prior published works involving 81,000 patients and 212,000 doctor visits yielded about 1600 records for analysis.
A misdiagnosis was determined by either an unplanned hospitalization (trigger 1) or a primary care physician revisit within 14 days of an index visit (trigger 2).
A quote from the paper [Emphasis added] : For trigger 1, 141 errors were found in 674 visits reviewed, yielding an error rate of 20.9%. Extrapolating to all 1086 trigger 1 visits yielded an estimate of 227.2 errors. For trigger 2, 36 errors were found in 669 visits reviewed, yielding an error rate of 5.4%. Extrapolating to all 14,777 trigger 2 visits yielded an estimate of 795.2 errors. Finally, for the control visits, 13 errors were found in 614 visits reviewed, yielding an error rate of 2.1%. Extrapolating to all 193,810 control visits yielded an estimate of 4,103.5 errors. Thus, we estimated that 5126 errors would have occurred across the three groups. We then divided this figure by the number of unique primary care patients in the initial cohort (81,483) and arrived at an estimated error rate of 6.29%. Because approximately 80.5% of US adults seek outpatient care annually, the same rate when applied to all US adults gives an estimate of 5.06%.
The diagnoses that were missed and the implications of the misses were not described, but one anecdote from a paper the study was based on mentioned carpal tunnel syndrome as one of the diagnoses.
Another quote from the paper: Although it is unknown how many patients will be harmed from diagnostic errors, our previous work suggests that about one-half of diagnostic errors have the potential to lead to severe harm. While this is only an estimate and does not imply all those affected will actually have harm, this risk potentially translates to about 6 million outpatients per year. [Emphasis mine]
Is a 14-day interval between the supposed miss of the diagnosis and an admission or a return visit really a huge problem?
Because we don't really know how many patients were actually harmed by these supposed diagnostic errors, we can't tell. If carpal tunnel syndrome was the delayed diagnosis, I'd say "probably not."
Half of the patients in the study were from a VA and the other half were from a large clinic cohort so these diagnostic error rates may not be generalizable to the entire population of the US.
The words "misdiagnosis" and "error" were used interchangeably. As the authors admit, every misdiagnosis is not necessarily the result of a physician's error.
Among the limitations of the study noted in the paper [but omitted from all news reports] was that it was not designed to identify the root cause of the delayed care or missed diagnosis. For example, reviewers noted many cases where delays in follow-up were beyond the control of primary care providers, such as difficulty obtaining timely appointments with specialists [which we now know is a huge problem at many VA hospitals], or patients failing to show up at scheduled appointments.
No doubt diagnostic errors occur, but this paper does not tell us how many people were seriously harmed, what the root causes of the errors were, who was responsible for the errors, or most importantly whether diagnostic errors really occur in 5% of Americans.