That's a good point about the SARM.
I used to also think that microdosing T to stay within physiological levels would enable one to evade positive test. Most men can inject 7-10mg of a medium-term ester T like enanthate or cypionate and stay in upper physiological range of normal levels (e.g., 700 ng/dl versus top end of 900 ng/dl) with spiking T/E ratio
But the Carbon Isotope Ratio test changed all that. Good article on on Velo:
"Danielson was busted by CIR, short for Carbon Isotope Ratio, a highly accurate test that is able to distinguish between naturally produced testosterone and its synthetic cousin using molecular weight. It is the first test able to detect the synthetic testosterone itself, rather than the body’s reaction to it.
The traditional method of detecting abuse of testosterone looks for an imbalance in the ratio of testosterone and epitestosterone. It is referred to as the T/E ratio test. A normal ratio for most humans is near 1:1. The World Anti-Doping Agency (WADA) considers a ratio over 4:1 to be a positive test. This has dropped in recent years — it was 8:1, then 6:1, and now 4:1. Floyd Landis had a ratio of 11:1 when he was nabbed by both the T/E ratio test
and CIR in 2006 with a sample taken during the Tour de France.
If administered at the right time, the T/E ratio method can be very effective. But testosterone/epitestosterone ratios return to normal quickly, even overnight if taken in the right doses. With the ban on overnight testing, which was only recently partially lifted, the test’s real-world efficacy drops considerably.
The T/E test simply looks for a physiological response to doping, rather than the product itself. That is its flaw.
CIR is effective but expensive — $400-700 per sample, nearly 10 times the cost of the T/E ratio test. Like the T/E test, CIR is also based on a ratio. Labs determine the quantities of carbon-12 and carbon-13, two isotopes, or types, of carbon, within an individual’s testosterone molecules. Synthetic testosterone has less carbon-13 than naturally occurring testosterone."