Athlete Biological Passport (ABP)

The passport inverts the logic of conventional testing. Rather than asking whether a prohibited substance is present in one sample, it asks whether a series of samples from one athlete is consistent with that athlete's own physiology. An adaptive statistical model builds personal expected ranges that tighten as samples accumulate, so a value unremarkable against a population reference interval can be improbable for that individual. Two modules are in routine use, a haematological one and a steroidal one.

The haematological module rests on haemoglobin concentration and reticulocyte percentage, combined into a stimulation index that moves in opposite directions under blood manipulation and its withdrawal. The steroidal module tracks ratios within the endogenous steroid profile, with isotope ratio mass spectrometry available to separate synthetic from endogenous origin. It entered routine use around 2009, the steroidal module later, and an expert panel rather than software reviews every flagged profile.

Its value is that it does not require catching the parent compound. Many agents clear in hours while their physiological effect persists for weeks, so a scheduled test can be negative on chemistry alone; a passport can still support a use violation with no adverse analytical finding at all. It also drives targeted testing, an abnormal profile triggering collection at a time chosen by the analysis rather than by a calendar.

Two things it is not. It is not a general peptide detector: the modules in routine use track blood and steroid markers, and no equivalent endocrine module operates routinely for growth hormone secretagogues. And it is not a black box that convicts on an outlier, since altitude exposure, illness, dehydration, plasma volume shifts and pregnancy all move haematological markers, which is why confounder review sits between the flag and any charge.