USADA is the organization that was brought into pro boxing by Floyd Mayweather, but to date they've only done Mayweather fights. The recent popped tests of Lamont Peterson and Andre Berto were caught by VADA, an organization that Golden Boy Promotions is now apparently distancing itself from, and since Golden Boy is the only promotional company routinely using extra drug testing in boxing, that means VADA could be essentially elbowed out.
USADA is more expensive, and some argue that VADA is more extensive. GBP and VADA had a big disagreement with how the Peterson case was handled, which led to Richard Schaefer calling them "unprofessional and disrespectful." VADA argued that they had no legal right to tell Golden Boy of the failed test earlier than they did, and that the process played out as it normally would.
USADA was recently contracted to do testing for the Winky Wright vs Peter Quillin fight on short notice, but then removed themselves from that fight and destroyed the taken samples.