Introduction: Techniques that assess percent reticulocytes (%retics) or hemoglobin (Hb) to detect erythropoiesis‐stimulating agents (ESA) use in athletes may be useful in evaluating ESA responsiveness in dialysis patients. However, within‐patient variation, appropriate transformation, or the relationship between the blood draw interval length and analyte variation are untested.
Methods: In a prospective, single‐arm trial, we determined Hb and %retics in 30 hemodialysis patients receiving stable ESA doses. Within‐patient results were evaluated for variance homogeneity and normality with and without transformation.
Results: Square‐root transformation (sqrt) of %retics produced the most constant variance (lowest r‐value for correlation between sqrt|normalized residuals| and fitted values: 0.018 highest P‐value 0.739) compared with log transformation (r = −0.198, P < 0.001) or no transformation (r = 0.215, P < 0.001) and showed the least departure from normality (highest P‐value: 0.002 vs. < 0.001 vs. < 0.001, respectively). Hb results did not improve with transformation. Within‐patient variance in both %retics and Hb increased with interval length between lab draws (P < 0.001).
Conclusions: Initial assessment of anti‐doping tool use in dialysis patient anemia management indicates square‐root transformation of %retics and adjustment for time between lab draw intervals for both %retics and Hb will be required.