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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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.