Interpretation of Erythropoietin and Haemoglobin Levels in Patients with Various Stages of Chronic Kidney Disease

BACKGROUND The production of erythrocytes is regulated by the hormone erythropoietin (EPO), which maintains the blood haemoglobin (Hb) levels constant under normal conditions. Human EPO is a glycoprotein hormone and its synthesis is controlled by the hypoxia-inducible transcription factor. The aim of this study was to establish EPO and Hb levels in patients with chronic kidney disease (CKD), as well as in control subjects, and to investigate the relationship between these parameters. METHODS This cross-sectional, observational study included 356 subjects with CKD divided into 4 subgroups according to their glomerular filtration rate (GFR). The control group consisted of 206 age and sex matched healthy subjects with GFR rate ≥90 mL/min/1.73 m2. EPO, Hb and serum creatinine levels were determined by using immunochemical and spectrophotometric methods. GFR was determined using the MDRD formula. RESULTS The CKD patients had significantly lower levels of haemoglobin (p<0.0005) and hematocrit (p<0.0005) compared to control group. Our results showed that Hb levels decreased, whereas serum creatinine increased with the increasing renal failure. The CKD patients in all four groups had significantly lower (p<0.0005) Hb levels, and significantly higher (p<0.0005) creatinine levels compared to the control group. The median EPO in group I and II were significantly higher (p=0.002; p=0.018), while median EPO in group III and IV were significantly lower (p=0.03; p=0.011) compared to the control group. CONCLUSIONS In patients with CKD, GFR positively correlated with Hb and EPO, while the correlation between GFR and serum creatinine was negative.