Total Convection Affects Serum β2 Microglobulin and C-Reactive Protein but Not Erythropoietin Requirement following Post-Dilutional Hemodiafiltration
Authors: Movilli Ezio , Camerini Corrado , Gaggia Paola , Zubani Roberto , Feller Paolo , Salviani Chiara , Facchini Annalisa , Cancarini Giovanni 
Published: August 2015

<b><i>Background:</i></b> Inflammation and increased erythropoiesis stimulating agents (ESA) requirement are frequently associated in patients on dialysis. On-line hemodiafiltration (ol-HDF), putting together high levels of diffusion, and convection could improve both conditions. However, it is still not known which depurative component plays a major role in determining this result. The aim of the study was to evaluate the role of convection and diffusion on long-term variations of serum β<sub>2</sub> microglobulin (&#x0394;β<sub>2</sub>M), high-sensitive C-reactive protein (&#x0394;hsCRP) concentrations, and ESA requirement (&#x0394;ESA) in ol-HDF. <b><i>Methods:</i></b> Seventy-three patients prevalent on high flux HD (hfHD) were studied. Thirty-eight patients were switched from hfHD to post-dilutional ol-HDF (Study group); the other 35 patients were considered the Control group. At 6 and 12 months, the effects of ol-HDF and hfHD on &#x0394;hsCRP, &#x0394;B<sub>2</sub>M, and &#x0394;ESA (U/kg/week) were evaluated. Other variables considered were body weight (BW), serum albumin (sAlb), hemoglobin (Hb), and equilibrated Kt/V (eKt/V). Iron therapy and ESA were administered intravenously according to the K/DOQI guidelines in order to maintain transferrin saturation between 20 and 40%, serum ferritin between 150 and 500 ng/ml and Hb between 11 and 12 g/dl. Qb, treatment time and Qd remained constant. Ol-HDF and hfHD were performed using membranes of size 1.9-2.1 sqm. Ultrapure dialysate and substitution fluid were employed in both HDF and HD treatments. Data are expressed as mean ± SD. Paired t test, Mann-Whitney U test, and simple and multiple regression analyses were employed for statistical evaluation. <b><i>Results:</i></b> Study group: total convective volume (TCV) was 22.1 ± 1.9 l/session. A significant reduction of hsCRP: from 6.8 ± 7.1 to 2.3 ± 2.4 mg/dl (p < 0.001), β<sub>2</sub>M: from 36.5 ± 14.4 to 24.7 ± 8.6 mg/dl (p < 0.0001) and ESAdose: from 107 ± 67 to 65 ± 44 U/kg/week (p < 0.005) was observed. No significant variations of Hb, BW and sAlb were seen. A significant inverse correlation was found between TCV and &#x0394;β<sub>2</sub>M (r = -0.627; p < 0.0001), and TCV and &#x0394;hsCRP (r = -0.514; p < 0.0001); no correlation between TCV and &#x0394;ESAdose was observed. No correlation was found between eKt/V and &#x0394;β<sub>2</sub>M, &#x0394;hsCRP, and &#x0394;ESAdose. Multiple regression analysis with &#x0394;ESAdose as dependent variable showed &#x0394;hsCRP as the only significantly associated independent factor (p < 0.01). Control group: no significant variations of hsCRP, β<sub>2</sub>M, and ESAdose were observed over time. <b><i>Conclusions:</i></b> Ol-HDF induces a long-term significant reduction in pre-dialysis β<sub>2</sub>M and hsCRP concentrations. The magnitude of reduction is directly correlated to the amount of TCV achieved but not on eKt/V. The observed reduction in ESAdose requirement is independent either on convection or diffusion, but is directly associated to the concomitant reduction of inflammation.