from steroidiculous dot com
Let me explain what a steroid test is***8230;.
The body produces testosterone and epitestosterone, two very chemically-similar hormones, in roughly equal quantities. In healthy adult males, the ratio of the two hormones in the body tends to sit somewhere around 1:1. The relevant difference between the two is that while testosterone has the usual litany of performance enhancing benefits, epitestosterone doesn***8217;t. So as you might expect, urine samples of athletes who have taken illicit testosterone supplements (or steroids that are metabolized into testosterone, like McGwire***8217;s androstenedione) often show large amounts of testosterone with relatively normal amounts of epitestosterone.
The first urine test that WADA will perform is a testosterone/epitestosterone ratio screening test, where a urine sample is chemically analyzed to find the ratio of the concentrations of the two hormones. WADA sets the test limit at 4:1. If an athlete***8217;s urine sample contains four times as much testosterone as epitestosterone, the sample is marked as a failed test. Failed steroid tests carry an enormous public stigma, so it***8217;s important to note that somewhere around 5 percent of the population of adult male professional athletes have a natural T/E ratio of 4:1 or greater. Since CDT collects a urine sample from everybody during spring training as well as 1,400 samples over the course of a season, this means that even if steroid use was completely eradicated from organized baseball, more than a hundred urine samples would fail the T/E test every year. This does not mean the player was taking any banned substances. WADA uses the T/E test simply as a culling process, not as a damning confirmation of steroid use.
If a player fails the T/E test, WADA moves onto what they call the confirmation test, an isotope ratio test. I***8217;m going to have to make one more detour into biochemistry here, but I***8217;ll try to keep it quick.
All carbon on the planet exists as a mixture of isotopes, different versions of carbon. Almost all of the carbon on the planet has six protons and six neutrons inside of the atom, which we call carbon-12. However, one percent of the carbon on Earth has an extra neutron, seven in total. We call this carbon-13, and it***8217;s ever so slightly heavier than your usual garden-variety carbon-12. All organic molecules have a significant quantity of carbon, so naturally, the carbon in your body will have a small amount of carbon-13 mixed in. For the most part, carbon-13 walks and talks just like carbon-12, but due to its relative heaviness, plants have been very, very slowly preferring carbon-12 over carbon-13 over several million years. Because of this tiny selection process, the carbon in living things is slightly higher in carbon-12 content than the rest of the carbon in non-living things.
The testosterone naturally produced by the body is made from material that was once a carbon-12 selecting plant (which was eaten by a cow which turned into your steak, for example), so it has a similar isotopic carbon-13/carbon-12 ratio. Testosterone produced outside the body comes from the world of pharmaceuticals, where the carbon hasn***8217;t been through the same million-year-old selecting cycle. Because of this, synthetic testosterone tends to be slightly richer in carbon-13 than natural testosterone. WADA uses an isotope ratio mass spectrometer to check the isotopic ratio of testosterone in a urine sample. If it deviates from natural testosterone by three carbon-13 atoms per thousand or more, it***8217;s marked as a failed test, which indicates the presence of exogenous testosterone.
So, as you can see, in order to do a steroid test, first, they take an offseason sample, compare that to a sample they take when they suspect you***8217;re geared up. If you fail THAT one, you have to take an isotope ratio test, which is performed by an extremely expensive gadget called an isotope ratio mass spectrometer. If you were being tested for steroids, you***8217;d know.