What Does it Mean if Primary Care Doctors Get the Answers Wrong About Screening Stats?
Last week the Annals of Internal Medicine published a new report on how doctors (don’t) understand cancer screening stats. This unusual paper reveals that some primary care physicians – a majority of those who completed a survey – don’t really get the numbers on cancer incidence, 5-year survival and mortality.
An accompanying editorial by Dr. Virginia Moyer, a Professor of Pediatrics and current Chair of the USPSTF, drives two messages in her title, What We Don’t Know Can Hurt Our Patients: Physician Innumeracy and Overuse of Screening Tests. Dr. Moyer is right, to a point. Because if doctors who counsel patients on screening don’t know what they’re speaking of, they may provide misinformation and cause harm. But she overstates the study’s implications by emphasizing the “overuse of screening tests.”
The report shows, plainly and painfully, that too many doctors are confused and even ignorant of some statistical concepts. Nothing more, nothing less. The new findings have no bearing on whether or not cancer screening is cost-effective or life-saving.
What the study does suggest is that med school math requirements should be upped and rigorous, counter to the trend. And that we should do a better job educating students and reminding doctors about relevant concepts including lead-time bias, overdiagnosis and – as highlighted in two valuable blogs just yesterday, NPR Shots and Reporting on Health Antidote – the Number Needed to Treat, or NNT.
The Annals paper has yielded at least two unfortunate outcomes. One, which there’s no way to get around, is the clear admission of doctors’ confusion. In the long term, this may be a good thing, like admitting a medical error and then having QA improve as a consequence. But meanwhile some doctors at their office desks and lecterns don’t realize what they don’t know, and there’s no clear remedy in sight.
Dr. Moyer, in her editorial, writes that medical journal editors should carefully monitor reports to ensure that results aren’t likely misinterpreted. She says, in just one half-sentence, that medical educators should improve teaching on this topic. And then she directs the task of stats-ed to media and journalists, who, she advises, might follow the lead of the “watchdog” HealthNewsReview. I don’t see that as a solution, although I agree that journalists should know as much as possible about statistics and limits of data about which they report.
The main problem elucidated in this article is a failure in medical education. The cat’s out of the bag now. The WSJ Heath Blog covered the story. Most doctors are baffled, says Fox News. On its home page, the Dartmouth Institute for Health Policy & Clinical Practice links to a Reuters article that’s landed on the NIH/NLM-sponsored MedlinePlus (accessed 3/15/12). This embarrassment further compromises individuals’ confidence in doctors they would and sometimes need rely on.
We lie, we cheat, we steal, we are confused… What else can doctors do wrong?
The second, and I think unnecessary, problematic outcome of this report is that it’s been used to argue against cancer screening. In the editorial Dr. Moyer indulges an ill-supported statement:
…several analyses have demonstrated that the vast majority of women with screen-detected breast cancer have not had their lives saved by screening, but rather have been diagnosed early with no change in outcome or have been overdiagnosed.
The problem of overdiagnosis, which comes up a lot in the paper, is over-emphasized, at least as it relates to breast cancer, colon cancer and some other tumors. I have never seen a case of vanishing invasive breast cancer. In younger women, low-grade invasive tumors are relatively rare. So overdiagnosis isn’t applicable in BC, at least for women who are not elderly.
In the second paragraph Dr. Moyer outlines, in an unusual mode for the Annals, a cabal-like screening lobby:
…powerful nonmedical forces may also lead to enthusiasm for screening, including financial interests from companies that make tests or testing equipment or sell products to treat the conditions diagnosed and more subtle financial pressures from the clinicians whose daily work is to diagnose or treat a condition. If fewer people are diagnosed with a disease, advocacy groups stand to lose contributions and academics who study the disease may lose funding. Politicians may wish to appear responsive to powerful special interests…
While she may be right, that there are some influential and self-serving interests and corporations who push aggressively, and maybe too aggressively for cancer screening, it may also be that some forms of cancer screening are indeed life-saving tools that should be valued by our society. I think, also, that she goes too far in insinuating that major advocacy groups push for screening because they stand to lose funding.
I’ve met many cancer agency workers, some founders, some full-time, paid and volunteer helpers – with varied priorities and goals – and I honestly believe that each and every one of those individuals hopes that the problem of cancer killing so many non-elderly individuals in our society will go away. It’s beyond reason to suggest there’s a hidden agenda at any of the major cancer agencies to “keep cancer going.” There are plenty of other worthy causes to which they might give their time and other resources, like education, to name one.
Which leads me back to the original paper, on doctors’ limited knowledge –
As I read the original paper the first time, I considered what would happen if you tested 412 practicing primary care physicians about hepatitis C screening, strains, and whether or not there’s a benefit to early detection and treatment of that common and sometimes pathologic virus, or about the use of aspirin in adults with high blood pressure and other risk factors for heart disease, or about the risks and benefits of drugs that lower cholesterol.
It seems highly unlikely that physicians’ uncertainty is limited to conceptual aspects of cancer screening stats. Knowing that, you’d have to wonder why the authors did this research, and why the editorial pushes so hard the message of over-screening.
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This paper has really important findings. Mistakes in the interpretation of screening tests might worsen a patient’s condition. He might be asked to take a wrong drug or undergo an unnecessary procedure. Doctors must also be well informed and train on proper ways to interpret screening stats
Yes there is a failure of medical education and much of this because medical schools are closely associated with practices where screening is part of a marketing strategy to attract paying patients who are essential well, but can be plugged into a clinical machine which generates all sorts of revenue from the downstream effects of screening. Screening programs all sorts of fundraising and “white hat” activities. At the present time, it is financially and politically unwise to recognize and teach skepticism of cancer screening. You might refer to it as just innumeracy. I call it strategic innumeracy.