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August 7th, 2008
11:27 AM ET

Is the drug testing process flawed?

By Dr. Sanjay Gupta

Chief Medical Correspondent

 

When an athlete is tested for banned substances, most of us have a certain expectation the result will come back positive or negative. And, based on that result, an athlete will either be innocent or guilty. But, it’s not even close to being that easy, according to a new article in Nature, written by biostatistician Dr. Donald Berry (Read study). Dr. Berry calls the science so "weak," it is often impossible to tell whether an athlete, who has tested positive for a banned substance, really doped or not. Even as a student of statistics, this was pretty amazing to me, so I decided to look further.  (Watch video)

 

Dr. Berry uses the example of Floyd Landis to make his point. Berry concurs Landis had an unusual test result, but argues that result is pretty meaningless. Here’s why:  because Landis provided 8 pairs of urine samples, and assuming an approximately 95 percent specificity, the probability of all 8 samples being labeled “negative” is the eighth power of .95 or just .66 (66 percent).

 

If that's a little too much math and science for you at this hour, here is the final conclusion: Floyd Landis’ test had a 34 percent chance of being a false positive! Remember, this is a guy who was stripped of his title and banned from competition for 2 years. All of that was based on a test that had a very high false positive rate. By the way, Landis maintains his innocence and claims he has never used illicit substances. 

 

To be fair, testing authorities will say they err more on the side of false negative than false positive. Of course, that means there are probably some cheaters out there who will never get caught. It is by no means a perfect system, and is made ever more complicated by designer drugs made specifically with the idea of being undetectable. 

 

So, what to do about this system of checking for doping? Based on the science, it hardly seems accurate enough - the more you test, the more false positives and negatives you will see. Is the idea of testing for banned substances too imperfect to be meaningful?

 

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soundoff (13 Responses)
  1. Susan

    Dr. Gupta:

    The sport of cycling is really dirty with doping. They know how to fake the tests out. Certain drugs used for performance enhancing will not be picked up in the tests. When seconds ( or smaller ) can determine the outcome some will use anything to get that edge.

    Susan
    Phoenixville,PA

    August 7, 2008 at 17:22 | Report abuse | Reply
  2. grace

    Doesn't science already have a method for this? Usually a 95% confidence level is used as a cutoff. In the given example, there is only 66% confidence that the results were a true positive.

    To nitpick a little, my understanding is that it's actually only on the condition if Landis were truly negative, there would be a 66% chance that all 8 samples would test negative. If Landis were truly positive, there would be a much smaller chance that all 8 samples would test negative.

    To evaluate the meaningfulness of a positive test result, you also need to know the sensitivity of the test and do a calculation with sensitivity. My understanding is that specificity measures how well the test classifies true negatives as negative. Sensitivity measures how well the test classifies true positives as positive. If the test is fairly sensitive, the chance that a person who is truly positive tests positive only 1 out of 8 times is probably very low.

    For example, let's pretend the sensitivity of the test is 95%. Then the chance that a person who is truly positive tests positive only 1 out of 8 times is 0.05^7 * 0.95, the seventh power of 0.05 multiplied by 0.95, which is something so low like 0.0000000.... Then you can easily see that if the test is sensitive, using 1 out of 8 as positive is quite wrong.

    It seems that it's the interpretation and understanding process that's flawed. No test can make up for how humans understand its meaning. If everyone involved in the drug testing process, or any medical testing process, had to take a math and statistics test to test their actual understanding of what the results and numbers mean, it sounds like we would see a lot of cause for concern.

    This type of skill is basically mathematical and computational logic. Do we need more training in that in medical schools and health professions?

    August 7, 2008 at 20:56 | Report abuse | Reply
  3. Thomas A. Fine

    It's not quite a fair characterization to say that his conclusion is that Landis has a 34% chance of a falsely positive test. The real conclusion is that without knowing what the false positive and false negative rates are, Floyd's chances COULD be that high or possibly higher.

    The point I think is that it's unconscionable to run an anti-doping program when you apparently have no idea what the odds are on the validity of your tests, for Landis or anyone else.

    I think I was most struck by the editorial that was linked to Berry's article. I was surprised that the editorial staff of Nature would so strongly agree with Berry, and so soundly thrash the current anti-doping regime.

    tom

    August 8, 2008 at 00:31 | Report abuse | Reply
  4. Ron Howerton

    I don't understand the big deal about doping. Millions have been spent developing swim suits that shape the body to reduce a swimmers performance by milli-seconds. Divers shave their body hair to reduce their splash. Bike riders shave body hair and wear special helmets to improve aerodynamics. Gymnasts wear special gloves and apply talc to improve their grip. Runners use special shoes with better traction, etc. Boxers trim weight to complete in a lower class. Just like doping, none of these actually make the competitor stronger, faster, or better than their competition.

    Whatever happened to competing based on skill? What is the value of a competition that can be won by simply developing a piece of equipment competitors cannot afford? What's the difference between doping and slimming the body's aerodynamics if they both result in a reduction in lap time without an improvement in the competitors actual performance? Isn't a technological advantage just legal cheating?

    The problem isn't doping. The problem is competitors who care more about winning than competing fairly. The ancient Greeks may have had the right idea about competing in the nude – at least their contests had more to do with strength, speed and endurence, than bio-engineering.

    August 11, 2008 at 14:37 | Report abuse | Reply
  5. Arya

    Grace said it best with, "No test can make up for how humans understand its meaning." That 34 percent represents false positives for eight samples, but not the whole sampling itself. One positive result comes hand-in-hand with seven negative results - hardly a convincing reason to accuse someone of doping.

    August 11, 2008 at 21:25 | Report abuse | Reply
  6. Praetorian, Fort Myers

    My concern is that most of the drug testing is conducted by the drug companies.

    There are no third-party testing services that test drugs. Clearly with little FDA oversight and test studies that are conducted and controlled by the pharmaceutical companies–who is really looking out for the interests of the end user with respect to: adverse reactions, costs.

    August 20, 2008 at 15:24 | Report abuse | Reply
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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.