Introduction: The therapeutic efficacy of erythropoietin (EPO) may be diminished by the formation of anti-erythropoietin antibodies (AEAs), potentially resulting in therapy failure. Objectives: This retrospective study included 84 hemodialysis patients with end-stage renal disease (ESRD) treated with recombinant EPO and aimed to evaluate the association between serum AEA and treatment response. Patients and Methods: This cross-sectional study included eighty-four Iraqi patients with ESRD who had been on recombinant human EPO for more than 6 months and had hemoglobin levels below 11 g/dL. Serum AEA levels were measured in all patients to evaluate their association with treatment response and to investigate correlations with demographic, clinical, and laboratory data. Results: The study found that 64.3% of patients displayed increased AEA levels (>20 ng/mL). A poorer hemoglobin response after two months (ΔHb) was associated with increased AEA levels (β = -15.21, P=0.002). Additionally, a higher erythropoietin resistance index (ERI) emerged as a significant positive predictor (β = 1.50, P=0.018), while lower serum albumin demonstrated a protective effect (β = -22.50, P=0.048). Conclusion: This study indicates a significant prevalence of AEA in patients with ESRD undergoing EPO therapy. Regression analysis revealed that a poorer hemoglobin response (ΔHb) and a higher ERI were independent predictors of elevated AEA titers, while serum albumin was a protective factor.
