Tuesday, November 11, 2008

Evidence-based medicine

On the fringes of medical knowledge, lives are at stake and medicine doesn't have the answers yet. What do you do?

As I've recently studied the nature of healthcare today, one thing I've learned about is evidence-based medicine. It's a discipline whose intent, at least in part, is to correct what you might call "medical superstition" - overprescribing certain treatments for no reason other than an individual doctor's preferences or superstitions.

Excellent researchers, now at Dartmouth, discovered widely varying practices, such as a fourfold difference in rate of certain surgeries (from tonsillectomies to hysterectomies) in some regions, even after correcting for differences in population. The discipline of evidence-based medicine is to prescribe treatments based on evidence that they make a difference, not based on local doctors' personal favorites.

What I'm also learning, though, is that the discipline has shortcomings. For one thing, not all evidence of effectiveness means something should be prescribed a lot. The End of Medicine cites Lipitor, the cholesterol drug (a "statin"). We spend $25 billion a year on statins. There's statistically significant evidence that it helps - a 35% reduction in coronary events. But that same evidence, if examined closely, shows that it only makes a difference for 0.5% of the population.

Specifically: 1.59% of the placebo group had a coronary event, but 1.03% of those who got a statin had one anyway. (n=19,243. Study=ASCOT-LLA.)

Looked at a different way: if you're over 60 with cholesterol over 240, you have a 51% chance of coronary disease sometime before you die. But 49% still don't. Which group are you in? Nobody knows: we're at the fringes of knowledge.

This reminds me of the situation with my cancer treatment, high dosage Interleukin-2 (HDIL-2). Depending on which study you read, it only works on 7%, 13%, or 20% of patients. At my hospital it works on 20%, and my team said that's largely because they've gotten better at predicting who it won't work on, so they don't even try. But still, only one in five responds.

End says we spend $25 billion a year on statins; this 2005 article says 12 million of us are on Lipitor, not to mention other statins. The 35% decrease is enough to make it justifiable to insurance companies and doctors. Think what else we could do with $25 billion a year.

Another limitation of evidence-based medicine is that if it's used as the gating criterion for using a treatment, it blocks many things that could be useful if you're in need now, and the firm evidence you need now has not yet been developed - or has been developed, and hasn' t been published yet. (See "the lethal lag time" in Chapter 5 of the e-patients white paper.)

Or it's been published and your doctor hasn't seen it yet. (Tens of thousands of peer-reviewed studies are published every year. Who can keep up?)

This comes up time after time in the book Anticancer, which I mentioned the other day. Sample quote from a woman at a breast cancer conference: "If we wait for you epidemiologists to decide what's what, we'll all be dead! We need to make our choices now."

This is not to say that evidence-based medicine is wrong. It's a valid method, but it needs to be understood for what it is, not swallowed blindly.


  1. Very enlightening, Dave. I've referred to this post in my take today at http://www.diabetesmine.com/2008/11/evidence-based.html.

    All the best,

  2. Great to hear from you, Amy!

    Here are two subsequent posts here that continue the discussion, with links to the further discussions on e-patients.net:

    Very important new article for anyone who wants to understand health statistics:

    Subsequent discussions:

    E-patients group member Sarah Greene, until recently the head of the NY Times online health presence, recently remarked "An e-patient doesn't get to wear that 'e' until they take responsibility for Educating themselves about Evidence." I couldn't agree more.

  3. Dave, this is a really excellent summary of the strengths and weaknesses of "evidence-based medicine." Bravo!

  4. Folks, we're honored to have a visit from the terrific Terry Graedon, co-owner of The People's Pharmacy, one of the prime "specimens" of an e-patient community discovered by Doc Tom Ferguson, the original e-patient doc.

    Doc Tom noticed People's Pharmacy and enlisted Joe and Terry Graedon to be among his advisors on the e-patient white paper. After Tom's death, they helped finish it.

    The power of patient communities reached a new level earlier this year when Joe and Terry accumulated many, many reports from their forum members saying that a particular generic drug was NOT having the same effect as the brand name. The FDA had never before agreed to investigate complaints against any generic, but the weight of data brought by the Graedons' users forced the agency to review the case. It was reported here on the e-patient blog and here in the Wall Street Journal.

    Needless to say, it's affirming and happy-making to get kudos from someone like that. Thanks, Terry, and y'all come back, y'hear?

  5. Evidence-based medicine is where the health care provider applies statistically significant and relevant evidence acquired through quality and valid clinical trials utilizing the scientific method, as I understand. The health care providers assess the risks and benefits of how they choose to treat or not to treat their patients. This paradigm of a practicing health care provider is to better predict the outcomes of their treatment of their patients. Such providers recognize the need for quality in medicine and place tremendous value on their patients' lives.

    This paradigm of restoring the health of others protects public health.

    There are three areas of evidence-based medicine:

    1. Treat patients according to what is reasonable and necessary based on the evidence that exists regarding the treatment options health care providers select.
    2. Health care providers review this evidence in order to judge and assess the best treatment for their patients.
    3. Recognize that evidence-based medicine is in fact a movement that emphasizes the usefulness of this method to practice medicine.
    Two types of evidence-based medicine:

    1. Evidence-based guidelines- Policies and regulations are produced to ensure optimal health care.
    2. Evidence-based individual decision making- This is how restoring the health of others is practiced by the health care provider.

    This is the preferred way by many, I understand, to practice medicine instead of medical guidelines, which are created from a combination of clinical studies in which conclusions are drawn to reflect national standards of care for a particular disease state.

    Guidelines were largely implemented during the 1980s. At times, these guidelines are privately sponsored, which makes them unreliable due to bias and without independent systematic review or quality considerations by others. Unlike evidence-based medicine, guidelines can have major flaws and inaccuracies due to toxic factors used to create such guidelines. In fact, most doctors do not follow medical guidelines, yet are rewarded by programs such as Medicare if they do follow medical guidelines that are established.

    Dan Abshear

  6. An additional calculation, in hindsight:

    - 12 million people are on statins, at a cost of $25 billion a year. That's about $2,000 per person.

    - As discussed above, 1 person in 200 benefits from statins. 99.5% are unaffected.

    - 60,000 people benefit. (0.5% of 12 million.)


    The cost per "avoided cardiac problem" is $25 billion / 60,000 = $416,667.

    Four hundred thousand dollars per avoided problem.

    And that's not to mention the side effects of the drug, such as severely painful leg cramps (experienced mostly by women, including my wife).

    Is this smart policy? Is it a smart personal choice for you?


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