Supplementary Material for: The Role of Erythropoietin Levels in Predicting Long-Term Outcomes following Severe Acute Kidney Injury

Introduction: Acute kidney injury (AKI) survivors are at an increased risk of chronic kidney disease (CKD), end-stage kidney disease, and mortality. Little is known about the effect of erythropoietin (EPO), a kidney-producing hormone, in post-AKI setting. We aimed to investigate the role of EPO as a predictor of long-term outcomes in post-severe AKI survivors. Methods: We performed a retrospective analysis of post-AKI cohort conducted between August 2018 to December 2021. Adults who survived from severe AKI stage 2-3 were enrolled. Serum EPO was obtained at 1 month after hospital discharge. We explored whether EPO level could predict long-term kidney outcomes at 12 months including mortality, kidney replacement therapy, doubling serum creatinine, and major adverse kidney events at 365 days (MAKE-365). Results: One hundred twelve patients were enrolled. Median EPO level was significant higher in non-survivors than survivors [28.9 (IQR 16.2-50.7) vs 11.6 mU/mL (7.5-22.3), p=0.003]. The best EPO level cut-off was 16.2 mU/mL (sensitivity 77.8%, specificity 62.1%). Serum EPO predicted 12-month mortality with an AUC of 0.69. Combining clinical model using age, baseline, and discharge kidney function with serum EPO improved prediction with AUC of 0.74. Multivariable analysis demonstrated that high-level of EPO group had significantly higher mortality compared with low-level EPO group (15.2% vs 3.0%, p=0.020). Hematocrit was significantly lower in high-level EPO group compared with low-level EPO group at 12 months (33.4±1.1% vs 36.0±0.9%, p=0.038). Conclusions: Plasma EPO appears to be a useful marker for predicting long-term outcome in post-severe AKI survivors.