Factors affecting anemia and erythropoietin resistance in patients under dialysis

Anemia, one of the most important morbidity causes in patients under dialysis, has been successfully treated by the use of erythropoietin (EPO). However, anemia is resistant to erythropoietin in some of the patients. In our study, we aimed to define clinical and laboratory factors leading to anemia and ertyhtropoietin resistance. Two hundred patients (100 male and 100 female, mean age: 45.1+/- 16.2 years, 100 patients under hemodialysis (HD), 100 under periton dialysis (PD), mean dialysis duration: 34.3+/-17.4 months) who were under dialysis programme at Başkent University Ankara Hospital were included in our study. Classical erythropoietin by subcutaneous route was administered to these patients. In addition to erythropoietin, B12, folic acid and parenteral or oral iron were also administered to these patients according to serum levels. Patients were divided in to two groups according to EPO dose above (group 1) or under (group 2) 200 U/kg. Age, gender, dialysis type (HD or PD), dailysis duration, positivity of antiHCV, renal transplantation history, use of ACEI and statins, oral or parenteral iron treatment history in the last 6 months, hemoglobin, hematocrit, MCV, serum iron, iron binding capacity, ferritin, transferrin saturation (TS), albumin, CRP, PTH, TSH, vitamin B12, folic acid levels were investigated in two groups. Hemoglobin, hematocrit, serum iron and TS were significantly low in group 1 compared to group 2 (p=0.002, p=0.002, P=0.0001, and p= 0.002, respectively). 88.9% of patients in group 1 was under HD programme and 88.9% of patients were under parenteral iron maintanance therapy (p=0.0001 each). Ferritin levels were normal or elevated and no significant difference was deteceted according to ferritin and other factors (p>0.05). Logistic regression stepwise method was used to analyze all parameters and being under HD programme was found to the most important factor affecting EPO need (p=0.0001). In order to eliminate the effects of infection and inflammation and to define other factors affecting EPO resistance, 43 patints with a CRP level> 10 g/dl were excluded from the study. After excluding these patinets, grouping of the patients were made according to albumin<3.5 g/dl and PTH level<450 pg /ml. Logistic regression stepwise method revealed that relation between hypoalbuminemia (p=0.04, RR: 2.72), hyperparathyroidemia (p=0.02, RR:5.0), being under HD programme (p=0.0001, RR: 25.95), and EPO resistance were statistically significant. In conclusion, our study has shown that, being under HD programme, functional iron deficiency besides absolute iron deficinecy, hypoalbubinemia and hyperparathyroidemia were the most important factors causing EPO resistance and the importnat role of TS in