The biologic passport is based on statistic calculations of individual variations in Hb and OFF-score. 

It helps determining whether a certain value is outside the limits of so-called physiological oscillations, which are defined normal and deprived of particular significance. 
Being "outside" such limits does not necessarily mean being doped, as several causes could be at play: pathologies, traumas, stress, arterial hypertension, altitude, fatigue, nutrition. 

The Authors of the biologic passport propose 2 thresholds : 

- one of simple SUSPICION (with the chance of the value still being physiological of 1/50) 

- a SANCTIONABLE one (with the chance of the tested value still being physiological of 1/500 *) 
* N.B.: this means that the chance of a « false positive » is one on 500, which is not negligible at all. 

Those athletes who show at least 1 suspicious parameter are simply monitored over time with frequent out-of-competition tests, while for those who are sanctionable the Authors suggest a "NO-START", that is a suspension more or less extended. 

With time, the biologic passport keeps on collecting data, and the more tests, the better the profile of the single athlete will be outlined, usually (but not always!) progressively reducing the range of possible physiological oscillations. 
This way it becomes possible to sanction past values, even several months back, when it was not yet possible to define the limits (it takes 6 tests to activate the calculations) or when the limits were wider. 
The problem is that the athlete may not always be able to remember if influencing factors may have occurred and altered the "abnormal" test. 

It may even occur that, while collecting the data, the physiological obscillations range may in fact widen, allowing the sanctioned value to become normal again. 

Now the UCI proposes to ban athletes (up to 4 years!) on the basis of the biological passport results. 
Notwithstanding the considerations mentioned above (fundamental, in my opinion), what GUARANTEES do cyclists have that the numbers imputed to them are truthful? 
Lab errors are anything but rare when it comes to evaluating hematologic parameters, such as Hb and reticulocytes. 
Test results are often reported back to athletes with weeks of delay, and may be subject to "adjustments". 

Who controls UCI’s work of protection of the athletes ? 

The UCI proudly mentions 9 "independent" experts; does that mean they are not being paid? If they are, then defining them independent is a bit of a stretch… 

Every sanctionable case should be evaluated also by experts representing the riders’ association, prior to presenting the case to the public or make provision for suspensions. 

OUT OF COMPETITION controls added to the passport are a remarkable deterrent to the use of doping substances, and this is certainly a very positive fact, but beware when utilizing variations in hematic parameters to sanction athletes.