Background: Posttransplant anemia (PTA) is associated with increased mortality and reduced graft survival in kidney transplant recipients. Erythropoiesis-stimulating agents (ESAs) are usually used to treat PTA. Hyporesponsiveness to ESAs could be related to prognosis in patients with chronic kidney disease (CKD). There are few reports regarding hyporesponsiveness to ESAs in kidney transplant recipients with PTA. Hyporesponsiveness to ESAs may be involved in the pathophysiology of PTA, possibly relating to risk factors such as iron deficiency, infections, and myelotoxic drugs. Iron deficiency has been reported as the main cause of hyporesponsiveness to ESAs. Previously, responsiveness to ESAs was estimated using an erythropoietin resistance index (ERI), and ERI≧9.44 was associated with high risk of all-cause mortality in a Japanese cohort study of hemodialysis patients. In this study, we analyzed ERI in kidney transplant recipients with PTA and without iron deficiency.
Patients and methods: A cross-sectional observational study was conducted to investigate ERI in kidney transplant recipients with PTA at Osaka Metropolitan University Hospital. Patients who received ESA to treat PTA from April 2020 to August 2022 were enrolled in this study. Patients with iron deficiency defined as ferritin<100 ng/ml and transferrin saturation<20%, and those with missing data were excluded. ERI defined as erythropoietin dosage per week divided by weight and hemoglobin value (U/kg/week/g/dl) was evaluated in 31 patients at our hospital. The ESA dosages of darbepoetin alfa and epoetin beta pegol (CERA) were obtained by multiplying the dosage of these ESAs by 200. The patients were divided into two groups by ERI level: low ERI group; ERI <9.44 and high ERI group; ERI ≧9.44).
Results: Ten patents were in the high ERI group, and 21 in the low ERI group. There were no significant differences in age, gender, eGFR, and body mass index (BMI) between the two groups. However, ERI tended to correlate with BMI (r=-0.35, p=0.054). Moreover, multiple liner regression analysis showed that ERI was associated with BMI after adjustments for gender and eGFR.
Conclusions: BMI is a marker of nutritious status in the general population and patients with CKD. ERI in patients who have PTA without iron deficiency may be related to nutritious status.