Scores:
(1) ON score: to detect current erythropoietin use
(2) OFF score: to detect prior use during the past 14 days
Parameters:
(1) hematocrit, as a decimal fraction
(2) reticulocyte hematocrit, as a decimal fraction (derived from multiplying the MCV of the reticulocyte pool by the number of reticulocytes)
(3) soluble transferrin receptor in mg/L
(4) serum erythropoietin (EPO) in mU/mL
(5) percent macrocytes as a number from 0 to 100 (usually in the range of 1-2)
ON model score =
= (3.721 * (hematocrit)) + (30.45 * (recticulocyte hematocrit)) + (0.1871 * LN(EPO)) + (0.1267 * LN(soluble transferrin receptor)) + (0.115 * LN((percent macrocytes) + 0.1))
OFF model score =
= (6.149 * (hematocrit)) - (92.87 * (recticulocyte hematocrit)) - (0.145 * LN(EPO))
where:
• One laboratory reported soluble transferrin receptor in nM. Two other laboratories reported it in mg/L.
Interpretation (based on Figures 3 and 4, Parisotto et al):
• An ON model score > 2.6 indicates an athlete currently using erythropoietin. The precise cutoff may vary based on conditions and analytical methods.
• An OFF model > 2 indicates an athlete who is not currently using EPO but who has used it in the past 14 days.
