The Athlete Biological Passport: Longitudinal Steroid Profiling
Individualized Baselines, Bayesian Flagging, and Catching the Microdoser
Evidence grade 5 of 5, Settled. Read how the Atlas grades evidence.
The written rationale for this grade is still being prepared.
- FDA
- Not an FDA matter; WADA-accredited program
- WADA
- Monitoring framework for S1 Anabolic Agents
Reference only. Not medical advice.
What can go wrong
For athletes, the lesson is that even sub-threshold or microdosed testosterone can disturb a longitudinal profile and invite confirmatory testing. For the marketplace, it again contradicts the notion that 'small, smart' dosing is undetectable, the passport is designed precisely to catch what single tests miss.
This is something to take to a clinician. The Atlas can tell you what is known about the athlete biological passport: longitudinal steroid profiling in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.
This entry focuses on the longitudinal logic of the Athlete Biological Passport (ABP), distinct from the chemistry of detection. Rather than judging a sample against a fixed population cutoff, the ABP builds each athlete's individual baseline from repeated measurements and uses a Bayesian (adaptive) model to flag deviations from that personal norm. The steroidal module (operational from 2014) tracks urinary markers including the T/E ratio and related steroid concentrations over time; the hematological module separately tracks blood markers for EPO-type doping. Serum testosterone and androstenedione were added to the steroidal module in 2023.
Instead of one threshold, the passport learns your normal, so a shift that is invisible against the population stands out against yourself.
What people take it for
What it is taken for. Approval, where it exists, covers only some of these.
How it works
The ABP collects an athlete's marker values over time and computes individualized expected ranges. A new value is judged against the athlete's own prior distribution, so even a within-population-normal result can be flagged if it departs from that individual's established baseline. The steroidal module's longitudinal view is what makes microdosing detectable: small, repeated testosterone doses that never breach a fixed threshold can still perturb the personal profile, prompting target testing and IRMS confirmation of exogenous origin.
Why longitudinal beats single-threshold testing
A fixed 4:1 T/E cutoff can be gamed, by microdosing under the line, or by genetic variants (e.g., UGT2B17 deletion) that hold baseline T/E low. The passport answers this by comparing each athlete to themselves: a steady low T/E that suddenly drifts, or a profile inconsistent with the athlete's history, triggers scrutiny even without crossing an absolute number. The ABP does not by itself convict; it directs resources, flagging atypical profiles for confirmatory IRMS and for expert-panel review. It converts anti-doping from snapshot testing into continuous surveillance.
What people get wrong
Often saidYou only get caught if you exceed a threshold
ActuallyThe passport flags deviations from your own baseline, so even sub-threshold microdosing can be detected over time.
Often saidThe passport itself bans athletes
ActuallyIt is a monitoring and targeting tool; sanctions typically rest on confirmatory tests (e.g., IRMS) and expert review.
Who profits, and who pushes back
Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.
At a glance
- Approach
- Individualized longitudinal baseline, not a single population threshold
- Statistical engine
- Bayesian/adaptive model flagging deviation from the athlete's own norm
- Steroidal module
- Operational 2014; tracks T/E and related urinary markers
- 2023 expansion
- Serum testosterone and androstenedione added
- Complement
- Hematological module covers EPO/blood doping separately
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about The Athlete Biological Passport: Longitudinal Steroid Profiling. A short entry is not a safe entry.
- Timeline. We have not built the dated record of research and regulatory events.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- How it compares. We have not set it against the alternatives.
- Children and teenagers. We have not checked what is known about younger people.
Sources
The studies below are named and described, but not linked. You cannot open them from here and check our reading against them, which means this page is our summary of the literature rather than a document you can verify. Weigh it accordingly until the links exist.
The studies that matter
ABP steroidal module operational2014
Enabled longitudinal urinary steroid-marker monitoring
Adaptive (Bayesian) ABP modelestablished
Flags deviations from an athlete's individualized baseline
Serum markers added to steroidal module2023
Extended longitudinal monitoring to blood testosterone and androstenedione
UGT2B17 deletion and individualized profiling2015
Showed why personal baselines outperform fixed ratio cutoffs