Sure, I could have been a lot more thorough, if I had several hours to devote to this post. I didn't need to. I pointed out the gap between the values the USPSTF used in their recommendation, and the values the FDA uses when regulating drugs. I think the gap is large enough that none of the factors you mention will come close to closing it. I suggest you take it on yourself to supply the figures if you think otherwise.

But you didn't accuse me of just being sloppy, or failing to account for some factors. You wrote (my emphasis):

You state your conclusion without quantifying the factors involved or showing the calculation you used to reach the conclusion. ... neither the report or your criticism provide any concrete quantification of those factors.

And that is a blatantly false accusation.

You further wrote:

you don't give a neutral reader any reason to suppose that your hidden assumptions and calculations

As I already showed you my calculations twice, I can't imagine what you are referring to. There are no hidden calculations. Missing calculations, maybe. Hidden, no.

You didn't introduce any new factors not mentioned in the original report

Why would I do that? I think you're missing the point. This is not an post arguing in favor of mammograms.

I think you're missing the point. I'm not arguing against mammograms. From what I've seen here I'm still agnostic. The point of my original post was primarily to note the discrepancy between the apparent confidence you have in the wrongness of the report's conclusion and my impression that you failed to make your case at all convincingly.

I'm not aware of having any particular prior opinion on this issue. I was aware that it had come up in the back and forth debate over health care but I had not consciously formed a strong opinion on it. My (probably biased... (read more)

Action vs. inaction

by PhilGoetz 2 min read30th Nov 200943 comments


2 weeks ago, the U.S. Preventive Services Task Force came out with new recommendations on breast cancer screening, including, "The USPSTF recommends against routine screening mammography in women aged 40 to 49 years."

The report says that you need to screen 1904 women for breast cancer to save one woman's life.  (It doesn't say whether this means to screen 1904 women once, or once per year.)  They decided that saving that one woman's life was outweighted by the "anxiety and breast cancer worry, as well as repeated visits and unwarranted imaging and biopsies" to the other 1903.  The report strangely does not state a false positive rate for the test, but this page says that "It is estimated that a woman who has yearly mammograms between ages 40 and 49 has about a 30 percent chance of having a false-positive mammogram at some point in that decade and about a 7 percent to 8 percent chance of having a breast biopsy within the 10-year period."  The report also does not describe the pain from a biopsy.  This page on breast biopsies says, "Except for a minor sting from the injected anesthesia, patients usually feel no pain before or during a procedure. After a procedure, some patients may experience some soreness and pain. Usually, an over-the-counter drug is sufficient to alleviate the discomfort."

So, if we assume biannual mammograms, the conclusion is that the worry and inconvenience to 286 women who have false positives, and 71 women who receive biopsies, is worth more than one woman's life.  If we suppose that a false positive causes one week of anxiety, that's a little over 5 years of anxiety, plus less than one year of soreness.

(I heard on NPR that the USPSTF that made this recommendation included representatives from insurance companies, but no experts on breast cancer.  So perhaps I'm barking up the wrong tree by looking for a cognitive bias more subtle than financial reward.)

I'm not shocked at the wrongness of the conclusion; just at its direction.  The trade-off the USPSTF made between anxiety and death is only 2 orders of magnitude away from something that could be defended as reasonable.  Usually, government agencies making this tradeoff are off by at least that many orders of magnitude, but in the opposite direction.  (F-18 example deleted.)

So, what cognitive bias let this government agency move the decimal point in their head at least 4 points over from where they would normally put it?

I think the key is that this report recommended inaction rather than action.  In certain contexts, inaction seems safer than action.

Imagine what would happen if the FDA were faced with an identical choice, but with action/inaction flipped:  Say you have an anti-anxiety drug, which will eliminate anxiety of the same level caused by a false-positive on a mammogram, in 15% of the patients who take it - and it will kill only 1 out of every 2000 patients who take it.  Per week.

Would the FDA approve this drug?  Approval, after all, does not mean recommending it; it means that the decision to use it can be left to the doctor and patient.  The USPSTF report stressed that such decisions must always be left up to the doctor and patient; by the same standards, the FDA should certainly approve the drug.  Yet I think it would not.

A puzzle is why we have the opposite bias in other contexts.  When Congress was debating the bank bailouts and the stimulus package, a lot could have been said in favor of doing nothing; but no one even suggested it.  Empirically, we have a much higher success rate at intervening in health than in economics.  Yet in health, we regulate actions as if they were inherently dangerous; while in economics, we see inaction as inherently dangerous.  Why?

ADDED: Perhaps we see regulation as inherently safer than a lack of regulation.  "Regulating" (banning) drugs is seen as "safe".  "Regulating" the economy, by bailing out banks, passing large stimulus bills, and passing new laws regulating banks, is seen as "safe".  Recommending or not recommending mammograms isn't regulation either way; therefore, we perceive it neutrally.