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Wednesday, October 4th 2006

You Can't Trust Anybody!

If I can’t trust a huge pharm company, who can I trust?! One pediatric cardiologist goes after “relative risk.”

[T]he way in which scientists and drug companies describe the benefits of many medications—by framing the question in terms of “relative risks”—systematically inflates their value.

[T]his pervasive way of describing clinical trials in medical journals—focusing on the “relative risk,” in this case of heart attack—powerfully exaggerates the benefits of drugs and other invasive therapies. What, after all, does a 31 percent relative reduction in heart attacks mean? In the case of [a] 1995 study, it meant that taking Pravachol every day for five years reduced the incidence of heart attacks from 7.5 percent to 5.3 percent. This indeed means that there were 31 percent fewer heart attacks in patients taking the drug. But it also means that the “absolute risk” of a heart attack for any given person dropped by only 2.2 percentage points.

Mark Twain (of if you’re a purist perhaps Benjamin Disraeli) once said there are lies, damned lies, and statistics. Which is why when I had to pick an AP math course in high school I took calculus (also, because Isaac Newton rocks).


After Studying His Calculus (I Made A ‘B’) I Can Safely Say Newton Would’ve Been In Favor Of Using Relative Risk

But apparently not all statistics are bad. The author argues that physicians should use a new metric in determining the benefit of drugs and other treatments. “Number needed to treat,”

The NNT was heralded as a new and objective tool to help patients make informed decisions. It avoids the confusing distinction between “relative” and “absolute” reduction of risk. The NNT is intuitive: To a savvy, healthy person with high cholesterol that didn’t decrease with diet and exercise, a doctor could say, “A statin might help you, or it might not. Out of every 50 people who take them, one avoids getting a heart attack. On the other hand, that means 49 out of 50 people don’t get much benefit.”

But this will never be a popular measuring tool, because big pharm won’t let it! Those bastards!

But drug companies don’t want people thinking that way; whenever possible, they frame discussions of drugs in terms of relative risk reduction.

The reason is simple: Big numbers encourage people, even those who should know better, to prescribe drugs. In 1991, researchers performed a survey of faculty and students in epidemiology at Harvard Medical School—a group that should understand health statistics. When they were presented with identical information about a drug in different formats, almost half had a “stronger inclination to treat patients after reading of the relative change,” or risk reduction, as opposed to the NNT.

The pediatrician goes on a tear,

Does your child have an ear infection? Your pediatrician obliges with a bottle of amoxicillin, but the NNT for antibiotics to shorten the duration of fever is more than 20; thus, at least 19 out of 20 parents force the stuff down their toddlers’ throats for no reason. Is your prostate enlarged? The NNT to avoid surgery is 18 if you take Proscar for four years. The drug costs $100 per month per person, so an insurer spends $86,400 to prevent a single surgery for enlarged prostate. Are you thinking of taking aspirin to help avoid a heart attack? The NNT is a lousy 208. Keep in mind that none of these figures include the risks of side effects.

But I hope he isn’t arguing with that last line that from a community health perspective that the risks of everyone taking statins outweighs the benefits with a NNT of 50. Or that even at an NNT of 208 aspirin isn’t worth it from a health perspective.

I don’t know how many people take aspirin (a helluva a lot) but there were 52 overdose deaths in 2000, and from an August literature review,

“….low-dose aspirin increases the risk of major bleeding 2-fold compared with placebo. However, the annual incidence of major bleeding due to low-dose aspirin is modest—only 1.3 patients per thousand higher than what is observed with placebo treatment. Treatment of approximately 800 patients with low-dose aspirin annually for cardiovascular prophylaxis will result in only 1 additional major bleeding episode.”

I don’t think we’re going to find many examples where everyday physicians using the NNT is going to uncover drugs where the health risks outweight the health benefits. But, that is kind’ve what the good doctor is implying in that quoted paragraph above.

His real beef however, even though he doesn’t come out and say is basically that these treatments aren’t cost effective. He’s talking about rationing. Well, I’ll give him some benefit, in part he’s talking about patients being able to be consumers, being able to effectively weigh the costs versus the benefits. Okay.

Two points,

In terms of public health if Dr. Sanghavi thinks the costs of giving statins to every patient outweighs their benefit then perhaps he’s undervaluing human life. And, yes, I actually said that as health care costs skyrocket upwards faster than Richard Branson’s ambitions (I will be on one of those flights one day…).

Finally, in terms of health literacy and the public and providers ability to understand and analyze risk-benefit I really question what kind’ve improvement using NNT will give us. Clearly relative risk is misunderstood by plenty of people. But saying something like, “50 people had to take this drug for every 2 who benefited from it,” greatly improves the conversation?

I’m afraid if patients and doctors currently overstate the value of a treatment by using relative risk that they’ll undervalue it using NNT. But maybe not…

Let’s just admit it: I really shouldn’t be trying to speak on this subject. But if you want to be further confused, we have the index for the NEJM where NNT was originally proposed (really, really useful), and brief looks at relative risk and number needed to treat.

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