Source: Zorzoli & Rossi, 2010; Zorzoli 2011
'So, what are you looking at?
The green blocks show abnormal samples where reticulocyte percentage is HIGHER than normal - either 2 to 2.4% (light green) or above 2.4 to 5% (dark green). Remember that a higher reticulocyte % means more immature blood cells, suggesting EPO use or blood removal. So quite clearly, in 2001 and 2002, you had a high percentage of samples that suggest EPO use - between 9% and 11% of all samples, and 80 to 90% of suspicious samples. No surprise there - this was the era of EPO use.
Then comes the introduction of the urine test for EPO in 2002, which I've shown with a blue line. Suddenly, things change - now, you see much larger pink bars. The pink represents LOWER than normal reticulocyte percentage - either 0 to 0.2% (dark) or 0.2 to 0.4% (light)
So clearly, the EPO test changed things - from 2003 to 2007, between 6% and 10% of samples had low reticulocyte %, and these tests make up 80 to 90% of the abnormal test results. Remember, this suggests blood doping, and a shift in practice after the EPO test was introduced.'
Science of Sport Full article here.....