Reticulocytes measurements
are not accurate most of the time, perhaps the interpretation is easier. Reticulocytes are one of the two elements in
the quick formula to flag a doping violation:
OFF-Score =
(Hemoglobina (g/dL) x 10) – (60 X √% reticulocitos)
The aim was to prevent
athletes from competing when their (HCT) or hemoglobin (HGB) values were higher
than the established limit, which was the same limit for all athletes
(population limit). For some sporting bodies it was considered as a medical
rule, while for others it was a competition rule. The UCI introduced it in March
1997, and athletes were subjected to tests at or during competitions but not
out-of-competition. Tests were conducted on the field, and the samples were
analyzed on site. During unannounced bloods tests, several haematological
parameters were measured, which included HCT, HGB, % reticulocytes (RET%) and
the calculation of the stimulation index or OFF-hr score (Hb [g/L] –
60*√Ret[%]) (OFF-score).
It is not easy to obtain the
software which takes into account the majority of the parameters because it is
limited to the certified labs. As
ordinary mortals, our only option is to have an Off-score which has the
disadvantage of measuring the reticulocytes:
Let’s see what Medscape says about it:
The automated
hematology analyzer can also report a measurement of reticulocyte-specific
hemoglobin content as mean reticulocyte hemoglobin content (CHr) or
reticulocyte hemoglobin equivalent (Ret-He), depending on the type of
instrument used. CHr and Ret-He, two comparable but not identical parameters,
give a snapshot of the functional iron available for incorporation into
hemoglobin within RBCs over the previous 3-4 days. [9] A
decreased value generally reflects reduced cellular hemoglobin content and is
reliable in identifying functional iron deficiency…
Note that the reference ranges for automated reticulocyte
count (absolute reticulocyte count), immature reticulocyte fraction (IRF), and
reticulocyte specific hemoglobin content (mean reticulocyte hemoglobin content
[CHr] and reticulocyte hemoglobin equivalent [Ret-He]) vary owing to the
different methods and different instruments used. Each laboratory should
determine reference values according to their own methods and instruments. A
comparison of different reference ranges as reported by different authors can
be found in a review published article by Piva et al. [3]
As far as we know, Paula Radcliffe
was scrutinized based on her Off-score:
On off-scores and doping, since you've probably seen that Paula
Radcliffe has released the three off-scores in question to the media. Here's a
quick summary of what it means (and doesn't):
Off-score is calculated
using Hemoglobin & reticulocytes (immature red cells). Specifically, the
equation is:
Off-score = Hb (g/L) -
(60 x sqrt(Retic %))
If Hb is high & Ret%
is low, then off-score is high, and vice-versa.
At some point, the
off-score gets so high, it is strongly indicative of doping (the 1 in 100, 1 in
1000 thing). For example, Shobhukova had an off-score of 153 (yikes). The
off-score can also be so low that it suggests doping, and these
"cut-offs" or limits are known.
Radcliffe's values (115,
110 & 109) lie either just below (2) or just above (1) the off-score upper
limit WHEN TAKING ALTITUDE INTO ACCOUNT.
That is, there is a
different 'cut-off' to deal with altitude cases, because altitude is known to
affect the blood. So a normal cut-off of 103 is increased to accommodate this
recognized possibility/explanation.
Anyway, the point is
that Radcliffe is NOT a Shobhukova type example, though her numbers are still
high.
Where it gets tricky,
however, is that off-score values are ONLY PART of the picture, which is why
releasing 3 off-scores is not conclusive of anything, even if they are close to
those cut-off limits.
That's because the whole
premise of the passport is to measure CHANGE over time, and so a value can be
"normal" and thus not flagged by itself, but when that value is
looked at relative to others, it may be marked anyway.
Because of this, a
'spot' off-score of 100 might be more suspicious than a value of 110, if the
preceding values were 70 vs 105, respectively. The biological passport software
does have an adaptive component that works out a sequence score, but we're
dealing here with "spot" off-scores.
The formula gives a lot of
value to reticulocytes and a variation of .5% is a huge difference. Measuring reticulocytes is not accurate, even
the definition of reticulocyte is not accurate, and variations are bigger than
0.5% from lab to lab. We should spend
our time and money educating athletes, instead of paying for research that is not
accurate.
