Inflammation, peritoneal transport, and response to erythropoietin in peritoneal dialysis patients

The aim of the present study was to examine the association between 4-hour dialysate-to-plasma ratio of creatinine (D/PCr), erythropoietin (EPO) responsiveness [EPO (U/week)/hemoglobin (g/L)], and C-reactive protein (CRP). Subjects were 54 prevalent peritoneal dialysis (PD) patients [mean age: 58 years; 30 women, 24 men; 28 with diabetes; 15 on continuous ambulatory peritoneal dialysis (CAPD); 39 on continuous cycling peritoneal dialysis (CCPD); mean Kt/V: 2.44]. In 17 patients, CRP was elevated (> 15 mg/L), and in 39 patients, 4-hour D/PCr was high or high-average (> or = 0.65). Mean hemoglobin (Hb) was 115.5 +/- 12.9 g/L; median EPO dose was 2800 U/week, and median EPO/Hb was 24.5. A nonsignificant negative correlation was noted between CRP and hemoglobin (r = -0.25, p = 0.07), but no correlations were seen between CRP and 4-hour D/PCr, or hemoglobin and 4-hour D/PCr. No correlation was seen between EPO/Hb and 4-hour D/PCr or CRP. Multiple linear regression (stepwise, alpha = 0.05) was performed with outcome hemoglobin and independent variables EPO [U/week (forced in)], percent transferrin saturation [TSAT (forced in)], age, sex, diabetes mellitus, serum albumin, CRP, time on PD, 4-hour D/PCr, normalized protein catabolic rate (nPCR), ferritin, intact parathyroid hormone (iPTH), aluminum, and angiotensin converting enzyme inhibitor (ACEI) use. Serum albumin (1.27, p < 0.01) and diabetes mellitus (-6.69, p = 0.04) were the only significant predictors of hemoglobin. With serum albumin removed from the model, age (but not CRP) became significant. These results do not support an association between peritoneal transport and EPO responsiveness, mediated by inflammation. The association between serum albumin and hemoglobin appears to be confounded by age more than by inflammation.