SHORT REPORT

Day to day variability in the transferrin receptor/ferritin index in female athletes

R Stupnicki¹, J Malczewska², K Milde¹ and A C Hackney³

¹ Department of Biometry, Academy of Physical Education, Warsaw, Poland
² Department of Nutrition Physiology, Institute of Sport, Warsaw
³ Applied Physiology Laboratory, University of North Carolina, Chapel Hill, NC, USA

Correspondence to:
Correspondence to:
Professor Stupnicki, Department of Biometry, Academy of Physical Education, Marymoncka 34, 00-968 Warsaw 45, Poland;
rstupnicki{at}awf.edu.pl

Objective: To determine the within subject (day to day) variability for variables reflecting iron status (concentrations of ferritin and soluble transferrin receptor (sTfR), and the sTfR/logFerr index) in female athletes during a training camp, and in female control subjects.

Results: The error for ferritin concentration was nearly twice as high in athletes as in controls, that for sTfR concentration was identical in the two groups, and that for the sTfR/logFerr index was about 50% higher in athletes than in controls.

Conclusions: The within subject, day to day error for the sTfR/logFerr index computed from data recorded for untrained subjects cannot serve as a reference value for training athletes. When the sTfR/logFerr index is used to monitor iron stores in athletes, an error value of 0.20 should be used, because determination of the index after a few days of rest may not be feasible.

Keywords: transferrin receptor; ferritin; iron status index; variability; female athletes

Abbreviations: sTfR, soluble transferrin receptor; logFerr, log ferritin concentration

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