<p>The concept of the biological passport is to evaluate, on an individual and longitudinal basis, the effects of doping substances and prohibited methods—blood doping and gene doping—on the body. Indirect biological markers can be measured and used to establish an individual's biological profile, when variations in an athlete's profile are found to be incompatible with physiological or medical conditions; a disciplinary procedure may be launched on the presumption that a prohibited substance or method has been used. As such, an athlete with a biological passport is his or her own reference.</p>