In every male body a certain ratio of the hormones testosterone to epitestosterone are produced on a daily basis. In a typical male, this ratio rarely goes over 4 parts testosterone to 1 part epitestosterone. Therefore, if an athlete were to inject exogenous testosterone into the body, testosterone levels would increase, but epitestosterone would not. This would dramatically changes the T:E ratio.
According to WADA if the ratio of testosterone to epitestosterone is greater than 4:1 (changed from 6:1 previously) it's considered evidence of possible doping and leads to further tests ... the key word is "further testing" This means it's not finalized. . . a Carbon-Isotope Ratio test or CIR test is usually performed at this point. This is how Tour de France Champion Floyd Landis was caught.
WADA's Code advices two different practices to determine if the increased T:E ratio is due to a physiological or pathological condition or to administration of exogenous hormones ... However, there are documented cases of non-doping athletes with T:E ratios greater than 6:1 ... In that case additional testing is required to determine the etiology of the elevated ratio
if an athlete's urine test produces a ratio that is above 4:1 ... at least three additional samples must be tested ... These may be samples that were previously collected and analyzed or unannounced future tests ... If the results are less than 30 percent for males and less than 60 percent for females ... then it's likely that the T:E ratio is naturally increased ... thus declaring the athlete's test as "Negative".
WADA doesn't consider genetic factors ... However, in several cases natural testosterone is high (greater than 4:1 ratio)... as documented and recorded in the following races:
Asians registered 3.8:1 in the tests after steroids were added to their urine samples ... i.e. they have more room for tolerance.
An epitestosterone urine concentration greater than 200 ng/mL indicates its misuse (some people try to take additional epitestosterone to correct the balance ... When officials detect this, a person is said to be "positive" for use of epitestosterone.
Testosterone to Epitestosterone was set at 6:1 by the IOC Medical Commission in 1982 as a final positive test ... however it changed recently to 4:1.
*Carbon-Isotope Ratio test (CIR test) is a test that determines whether the extra amount of testosterone in the urine is endogenous (naturally produced) or exogenous (pharmaceutically taken).
The carbon isotope ratio is the ratio of two variants of carbon-carbon-13 to carbon-12 (these numbers indicate the atomic mass of the carbon which is the total number of protons and neutrons found in the nucleus). C-12, contains 6 protons and 6 neutrons, whereas, carbon13 contains 6 protons and 7 neutrons.
The measurement for pharmaceutical testosterone ... which is synthesized from plant steroids, is different from natural testosterone because the molecular carbon framework is put together differently by plants and humans. Pharmaceutical testosterone contains less carbon-13 than endogenous testosterone.
As you can see, the drug testing protocols are very scientifically specific and without a knowledge of this science, it becomes very easy to fail sports-specific drug tests.