to answer my own question:
Blood tests came into effect in 2000 to enable drug testers to confirm when artificial EPO is abused by athletes. While EPO can be detected in urine tests, the window of opportunity is very small – the testers have to take the sample within days of an athlete using it – but a blood test can raise suspicions about an athlete to help drug testers target subsequent testing.
HGH is only detectable in a blood test, as is the evidence of illegal blood transfusions, also known as blood doping.
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clearly blood tests are better than urine tests and a blood testing program should be set up in east africa pronto.