Background: Strict control of serum calcium and phosphate concentrations is paramount to prevent secondary hyperparathyroidism in haemodialysis (HD) patients. Standard intermittent low-flux HD (Lf-HD) is not sufficient to reach this goal. The aim of this study was to evaluate the effect of on-line haemodiafiltration (Ol-HDF) on serum calcium (sCa), phosphate (sPO4) and parathyroid hormone (PTHint) concentrations.
Methods: Of the 220 patients screened, 65 met the inclusion criteria for the study; 30 of whom agreed to participate in the study (Study group), the others were considered as the control group (Controls). Protocol for Study the group consisted of 6 months conventional Lf-HD (Period 1) and 6 months of post-dilutional Ol-HDF (Period 2). Controls continued their usual Lf-HD and were followed for 12 months. The main variables evaluated at the start and at the end of each period were sCa, sPO(4) and PTHint.
Results: The switchover from Lf-HD to Ol-HDF resulted in a significant reduction of sPO4 (from 5.1 ± 1.0 to 4.0 ± 0.7; P < 0.0001) and PTHint concentrations (from 307 ± 167 to 194 ± 98; P < 0.0001), no significant changes were found in both sCa concentrations (from 9.1 ± 0.7 to 8.9 ± 0.6) and phosphate binder dose. Kt/Vurea increased significantly, and beta(2) microglobulin concentrations decreased significantly. In the Controls, no significant variations of the same variables were observed over time, except for a significant increase in sevelamer intake.
Conclusion: This study supports the idea that Ol-HDF could be better than Lf-HD in controlling mineral metabolism in HD patients.