This article is the last in a series (Part 1, Part 2, Part 3) discussing BioPassport data posted on Livestrong.com. The focus will be on the persistent low normal Retic values from 6/16 through the end of the Tour.

Why is a persistent low normal Retic important?

Reticulocytes are a marker of Red Blood Cell production. There are normal swings in Retic. However, a persistently high or low Retic is an indication that the body is trying to compensate for a persistent deficit or surplus of Red Blood Cells (Hgb mass/oxygen carrying capacity).

An unusually low or persistently low Retic indicates artificially manipulated surplus of RBCs. It can be a marker of exogenous EPO (during the washout period) or of blood transfusion.

The main natural factors that affect Retic are training status and altitude exposure.

Training typically causes an initial increase in Retic followed by a slight decrease over the course of the season.

Altitude exposure results in a potentially greater rise in Retic followed by a greater fall before returning to baseline over a shorter period of time. (Note that altitude studies show a range of effects on Retic from no response to effects lasting 1 or 2 weeks after return from altitude, an interesting discussion for another day.)

Even when Hgb and OFF score are within normal limits, it is still worthwhile to look at Retic. Because it is not affected by volume status, Retic may sometimes be a marker of manipulation even when Hgb is well within the normal range. (scroll down until you see a box of data)

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This chart shows the average Retic for three periods, Pre – Grand Tour, 4/30 through the Giro, and 6/16 through the Tour.

Is the low normal Retic the cumulative effect of a long season?

The modest drop from Pre-GT to the Giro is consistent with a training effect.  The larger drop during from the Giro to the Tour is less easily explained by a simple training effect.

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Next the Giro and Tour trends are compared.

Is the drop the result of riding a Grand Tour?

This comparison is difficult to make because the Retic is at the opposite end of the spectrum at the start of each tour, Giro 1.3, Tour 0.5. Ultimately, this comparison does not explain the Tour values.

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Finally, this last chart shows a possible predicted  effect of altitude exposure.

Can a response to altitude account for the Retic?

Since Lance Armstrong is known for responsiveness to altitude, an effort was made to find best fit data from a group of “responders.” The Toluca 2000 data (Ashenden et al.) was gathered from a group of track cyclists who where followed over the course of a 25 day altitude camp, and two weeks after returning from altitude. This data was chosen for this article chosen because the group shows good responsiveness to altitude. Retic initially rises modestly above baseline then falls to a low point 1 week after return from altitude.

The composite chart above was constructed by superimposing the Toluca data over Armstrong’s taking care to line up altitude exposure. The Toluca curve required a significant downward adjustemnt to all the points so that the low points match up (Toluca baseline was 1.3) The idea behind the composite chart here is to get a sense if the trends might be consistent with those previously seen in response to altitude exposure.

What becomes evident from the composite prediction is that a rise in Retic between the end of the Giro and 6/16 may have been missed. The low Retic at 6/16 may be consistent with the fall after an initial peak. Similarly, the low point at 1 week after altitude exposure may be consistent with the low point after altitude exposure. Overal, assuming that the Retic did in fact trend up before falling you end up with a somewhat akward but plausible fit.

The explanation becomes less convincing when the Retic stays flat after reaching its low. The Retic does show a recovery, but it comes a week later than expected and is followed by another drop. In the end, altitude could be used to account for the initial drop in Retic, but it is not a solid explanation for a persistent low normal Retic.

Taking into account training status, the effect of a Grand Tour, and altitude exposure the analysis fails to fully explain the persistently low normal retic from 6/16 through the Tour. While other factors may be at play they probably have less of an impact. There is also the possibility of a synergistic effect, but it would be difficult to find data that supports this argument while excluding the possibility of manipulation at the same time.

In this series an attempt was made to aproach both sides of the discussion with a healthy scepticism. The result of this aproach was not a black and white answer. Instead, what is left are some unusual values that have not been adequately explained by the natural factors considered. Manipulation is not a conclusion that should be drawn lightly or without substantial proof. However, it should not be completely taboo and out of bounds either to discuss. Given cycling’s history, doping is simply a possibility that needs to be considered whenever results are otherwise difficult to explain.