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Understanding the Bio-Passport: Horner Values During Vuelta 2013

October 28, 2013

A large amount of attention has been given to Chris Horner’s release of his biological passport records from 2008-2013.  This is, to my knowledge, the most extensive, longest term set of bio-passport records ever released by a single athlete.  They have generate a lot of interest, with a number of blogs (Velo-clinic, Bike-rack-heads, JournalVelo, and VeloNation) and even Outside Magazine pointing out what they feel are things that Mr. Horner should explain.  Several of these analyses (though not all), share two common themes, themes that I believe are in error.  These problematic themes are:

  1. Many focus largely on the notion that Hemoglobin (Hg) should demonstrate a gradual decline over the duration of a grand tour, and that any “rebound” during the latter half of the tour is indicative of suspicious activity, or at best indicator that a “rebound” or “V-shaped” Hg trend is the characteristic of a small minority.
  2. They fail to look at the interaction between Reticulocyte Percentage (%R) and Hg when raising concerns about low-%R an blood-doping.

The first idea, that a rebound is suspicious or rare, is contradicted by the study of over 200 athletes during the Giro Bio (mentioned in a previous blog) which suggests that a rebound is, in fact, the norm rather than the exception.  The second, looking at low %R in absence of the corresponding Hg values is one that gets to the heart of bio-passport profiling and the OFF-score (a bit on that here).

Interplay Between Reticulocytes and Hemoglobin
I am going to attempt to provide some objective context to the 2nd issue, that of evaluating the Hg and %R in isolation of one another by describing the trends in the two data sets (Hg versus %R) and how they relate to one another.  I am not a hematologist, so I will try to refrain from making a conclusion about this data.  However, as a data analyst, I think that it is possible to put forth an objective set of observations about these two series and how they pertain to what is commonly understood as the basic underlying processes of red blood cell production.  I will refrain from discussing the absolute values of these numbers in context of what is “normal”, except to note that Horner’s OFF-scores in this 5 sample set ranged from 90.91 to 106.53, all within the current WADA guidelines for normal variation.  I will first present my description of individual trends, then present my observations about the interaction of those two trends, finally, I will present my thoughts about how that interaction relates to basic concepts of RBC production in the form of a question to hematologists or blood doping experts.

Descriptions of overall data trends

horner_HgRpct_vuelta2013_lg
The following observations are pertaining to Horner’s anti-doping tests around the time of the 2013 Vuelta (depicted in Figure 1 above).  The first test occured 2 days prior to the start of the race, and the subsequent 4 tests occurred between the 5th and 20th days of racing.

  1. Both Reticulocyte % (R%) and Hemoglobin (Hg) values are at their highest (0.85 & 15.2) at the first sampling date, 2 days before the start of the 2013 Vuelta.
  2. Reticulocyte percentage (%R) are at their lowest observed level on day 5 of the race (0.39), by the 9th day of the race they have climbed back up to 0.55 and then stabilize 0.55-0.56 for the remainder of the race.
  3. Hg values are at their lowest observed level on the 9th day of the race at 13.5.
  4. Hg values climb  back up by the 13th day of the race and stabilize somewhat, varying between 14.3 and 14.6 during the last 8 days of the race.

Interactions between the 2 data series

  1. Decreases in %R occur before Decreases in Hg – The lowest %R sample was 3 days before Hg reaches its lowest point.
  2. Increases in %R occur before increases in Hg – %R begins to rebound on the same day as Hg values are at their lowest level, with the largest increase in Hg taking place 4 days after the largest increase in %R.

The Chicken and the Egg
The following are based on a single underlying concept about Red Blood Cell (RBC) production:

Given – It is understood that it takes approximately 4-7 days (as described here & here) for the full life cycle from initial production in the bone marrow to RBC, with the transformation from the stage known as a “reticulocyte” to the mature, fully functioning RBC taking about 2 days (as noted in Guyton’s “Physiology of the Human Body”).

Observations/Questions for Hematologists
If this life-cycle time period is true, then I would suggest that following:

  1. A lag-time between the production of new RBC’s and increasing Hg concentration, as shown in the latter part of the race, seems to conform to the basic principles of RBC production.
  2. Since RBC-enriched blood transfusions suppress reticulocyte production, and Horner’s Vuelta drop in %R occurs along with a drop in Hg, wouldn’t this be counter to the effect that would be expected if Horner were transfusing enriched blood?
  3. Has there been some follow-up research that shows approx. 95% of athletes in Grio-Bio having an Hg rebound in the latter part of a grand tour to be irrelevant or flawed?

None of this is to say anything about whether Mr. Horner was doping during the 2013 Vuelta, or if he has ever dabbled in the Dark Arts.  But it is important, I think, to view data as an integrated whole, as opposed to in isolation, which is the whole point of the Bio-Passport.  Context is key.

Disclaimer: I am not a physician, hematologist, anti-doping expert, or even a veterinarian.  I am just a coach and athlete who has a passion for data analysis, visualization and clean and fair sporting.

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