Pro-inflammatory cytokines: a possible relationship with dialytic adequacy and serum albumin in peritoneal dialysis patients

Background: Inflammation and serum albumin concentration are both important predictors of survival in patients treated with peritoneal dialysis (PD). Furthermore, systemic and local inflammatory mediators may induce structural and functional alterations in the peritoneal membrane, thus interfering with dialysis adequacy. PD adequacy is monitored primarily by indices of small solute clearance, such as Kt/V urea and weekly creatinine clearance (wCc). The aim of this study was to investigate the possible relationship between pro-inflammatory cytokines, such as interleukin-6 (IL-6) and interleukin-1 beta (IL-1 beta), and serum albumin and C-reactive protein (CRP). Moreover, the relationship between IL-6 and IL-1 beta and PD adequacy has been analysed. Methods: We enrolled 46 stable PD patients undergoing maintenance PD for a minimum of 3 months. Plasma levels of serum albumin, high-sensitivity (hs)-CRP, IL-6 and IL-1 beta were measured in all patients. We used weekly Kt/V urea and wCc to monitor PD adequacy. Daily urine volume was measured in all patients. Results: The median values of serum albumin, hs-CRP, IL-6 and IL-1 beta showed no significant differences between continuous ambulatory PD and automated PD patients. IL-6 levels showed a positive correlation with hs-CRP levels (P < 0.001) and a negative correlation with serum albumin concentration (P = 0.01). There was no statistically significant relationship between IL-1 beta and hs-CRP or serum albumin concentrations. Subsequently, PD patients were divided into two groups based on Kt/V urea value. PD patients with Kt/V <= 1.7 had significantly higher IL-6 levels compared with PD patients with Kt/V > 1.7 (P = 0.015). No statistically significant relationship between IL-6 and wCc was observed. There was no significant difference in IL-1 beta levels between PD patients with Kt/V <= 1.7 and with Kt/V > 1.7 [median (interquartile range) 0.82 (0.88-5.2) versus 1.82 (0.95-2.7)]. There was no significant difference in IL-6 and IL-1 beta levels in PD patients with and without residual diuresis (P = 0.32 and P = 0.77, respectively). Conclusion: Our data suggest a possible relationship between serum IL-6 levels and serum albumin and hs-CRP in PD patients. Furthermore, IL-6 seems to be higher in patients with lower Kt/V, thus suggesting a possible use of this inflammatory biomarker in PD adequacy monitoring.