Applied Statistics

Tyler Cowen writes:

Breaking a three-day stalemate, the Senate approved an amendment to its health care legislation that would require insurance companies to offer free mammograms and other preventive services to women.

The vote was 61 to 39, with three Republicans joining 56 Democrats and the two independents in favor.

This happened directly after the release of evidence showing that many mammograms do not pass a comparative effectiveness test. Once the test became a public issue at all…well, now you see what happens.

It’s a problem when one branch of the government recommends less screening and then another branch recommends that all screening be made free. As Cowen notes, it’s even worse than that, in the sense that it was the reduced-screening recommendations that got the controversy started and led to the free-screening mandate.

But the story is a bit more complicated, if you get into the details of the politics and the decision analysis.

First, the politics. This is getting pretty confusing to me, because the last I heard, it was the Democrats who were supporting guidelines to limit mammograms for women under 50, and it was the Republicans who were leading the fight to disregard those recommendations. None of this makes sense to me.

Second, the decision analysis. The interesting thing about the comparative effectiveness studies is that mammograms aren’t really all that expensive. The key reason that mammograms for most women under 50 fail the comparative effectiveness test is that the tests are likely to result in false positives, causing unnecessary pain and anguish to the women thus affected.

The reason I’m bringing this up is that, to a large extent, the new recommendations imply that for younger women without risk factors probably shouldn’t want frequent mammograms even if they’re free. At least, whenever I’ve seen guidelines about this sort of thing, cost issues are downplayed. (For example, in the National Cancer Institute recommendations, the question “How much does a mammogram cost?” is answered as follows:

The cost of screening mammograms varies by state and by facility, and can depend on insurance coverage. However, most states have laws requiring health insurance companies to reimburse all or part of the cost of screening mammograms. Women are encouraged to contact their mammogram facility or their health insurance company for information about cost and coverage.

The recommendations really seem to be set up without considering the dollar cost of the procedure. So if people really do follow the recommendations, it’s not clear that much is lost by making the mammograms free.

This same argument goes for other moderately-priced health care items, I think. If certain forms of medical care are overused by some people, then I agree there’s something counterintuitive about turning around and offering them for free. But it’s not clear to me that it’s actually such a bad idea.

P.S. To put it another way, what seems more important to me is not who pays the small cost of a mammogram, but, rather how often people choose to have mammograms. Currently, lots of simple procedures are billed at many thousands of dollars even though the underlying cost is low.

P.P.S. To put it yet another way, even when medical procedures are free or nearly so, it’s not like people are going to the doctor and getting scans all the time.


  1. #1 Harlan
    December 5, 2009

    Yeah, I agree. It’s not like mammograms are a *fun* procedure, from what I’ve heard. I think it’s a better policy for preventive procedures and screening to be universally free for patients, and use other incentives to reduce health care costs and over-screening. Better statistical education for doctors, for example.

  2. #2 Gaythia
    December 5, 2009

    Even if the procedures were “free”, the radiologists and the mammography clinics would still be paid. That would potentially give some medical professionals a strong vested interest in increasing the number of mammography scans given.

    Also, fear of cancer is a strongly emotional thing, I’m not sure that it is always conducive to rational decision making.

  3. #3 Dylan
    December 5, 2009

    I wonder if we agree with Tyler’s intentions for quoting the article. I think he was just using the event to gauge for future success in price reduction by reducing payment for unjustified procedures. The reasons you gave would make cutting payment for mammograms for those not at one of the easier battles to win. Thus we shouldn’t be too hopefully the government will make long term strides in reducing costs.

    At least that’s what I think he is getting at.

  4. #4 Orac
    December 6, 2009

    As someone who is involved in the running of a breast center, I can tell you that screening mammograms are not that profitable at all. In fact, it’s hard to recruit new radiology residents to become mammographers because the liability is high and the reimbursement is low. In some facilities, screening mammograms are a break-even (if that) service. Where facilities make their money is in doing diagnostic mammography and ultrasound and, in particular, doing stereotactic (mammogram-guided) or ultrasound-guided biopsies of abnormalities.

  5. #5 Andrew
    December 6, 2009

    Screening may not earn profits, but treating false positives is profitable for doctors, and risky for patients.

  6. #6 jme
    December 6, 2009


    I feel like your comment leaves out an important point that is alluded to by Andrew in comment 5. Namely that screening mammography necessarily increases the amount of diagnostic mammography done. So to say that screening mammography loses money obscures the possibility (probably varies from provider to provider) they recoup that money and more in the extra procedures they generate in diagnostic mammography.

    It seems slightly dishonest to suggest (I don’t want to put words in your mouth, but the way you phrased your comment seems to imply this…) that screening mammographies are done with no regard to financial considerations when they obviously generate more business on the “profitably” side of things.

    I’ve been told that this is in fact why blood tests are routinely done in batches now, rather than individually. Hospitals discovered that while it _seemed_ like they’d be losing money by doing 12 tests for the price of 3, forcing the extra 9 tests generated so many extraneous “unusual” results that required follow up work that they easily made more money.

  7. #7 Michael Bishop
    December 6, 2009

    You seem to be arguing that the decision to require mammogram coverage might not be too harmful, rather than arguing that it is, or even could be, helpful. Am I missing something?

  8. #8 Matt
    December 6, 2009

    In the uproar over the new mammogram screening recommendations another reason was presented in defense of the new guidelines. This is that two new studies find no change in mortality with prostate screening. The conclusion being drawn is that cancer may not be fatal and that treating the cancer may cause unwarranted complications, cost, stress, etc.

    All of this is at odds with the wide spread support for pink ribbon campaigns to ‘fight’ breast cancer and celebrate breast cancer ‘survivors’. Combining their effects leads to incongruous outcomes like the Senate Amendment.

  9. #9 Andrew Gelman
    December 7, 2009

    Michael: Requiring mammogram coverage isn’t the same thing as requiring mammograms. If making them free (or available at a low cost) moves the patient’s and doctor’s decision away from dollars and toward the larger health costs and benefits for the individual patient, this could be a good thing. Or maybe not: providing something for free could lead to overuse. What I’m saying is that it’s not clear what’s the best way to go, in total.

  10. #10 wei
    December 10, 2009

    is there any markovian property of mammogram? Or will a series of negative results suggest a longer interval for the next scan?

New comments have been disabled.