Are there any numbers on how many riders in the peloton are diagnosed with exercise induced asthma? 1/3 of Sky riders is, after a quick Google scholar search, high (average from one study of elite athletes was 26% [self-diagnosis was 39%]; a guardian article reports that 70% of swimmers have asthma! theguardian.com/society/2014/dec/28/asthma-elite-athletes-study-swimmers-cyclist-eid)
I would say there's a pretty good chance asthma medication is being abused amongst elite athletes.
tests themselves may report above average positive hits:
"the heavy training with the extremely high level of physical fitness and maximum oxygen uptake (V’O2max) reached nowadays by elite athletes, may make it difficult to discriminate between physiological and pathological limitations to maximum exercise. This underlines the need for developing good diagnostic criteria for EIB and BHR in relationship to sports."