One of the two labs, which the researchers refer to as Lab B in their paper, never declared any sample positive, even when the men were taking high doses of EPO every other day. Lab A was inconsistent. It found EPO during the high dose phase. But in the maintenance phase, it found EPO in only 6 of the 16 samples.
It is not terribly surprising that the labs disagreed, researchers said. The EPO test, like urine tests for other hormones, including growth hormone, is extremely difficult. The lab must look for tiny chemical differences between the EPO a person makes naturally and EPO that is injected as a drug. ..."