Comparison of the pre-dilution and post-dilution methods for online hemodiafiltration

Online hemodiafiltration (OL-HDF) is a treatment modality using diffusion and ultrafiltration. There are two types of dilution methods in OL-HDF: pre-dilution, which is commonly provided in Japan, and post-dilution, which is commonly provided in Europe. The optimal OL-HDF method for individual patients is not well studied. In this study, we compared the clinical symptoms, laboratory data, spent dialysate, and adverse events of pre- and post-dilution OL-HDF. We conducted a prospective study of 20 patients who underwent OL-HDF between January 1, 2019 and October 30, 2019. Their clinical symptoms and dialysis efficacy were evaluated. All patients underwent OL-HDF every 3 months in the following sequence: first predilution, post-dilution, and second pre-dilution. We evaluated 18 patients for the clinical study and 6 for the spent dialysate study. No significant differences in spent dialysates regarding small and large solutes, blood pressure, recovery time, and clinical symptoms were observed between the pre- and post-dilution methods. However, the serum a1-microglobulin level in post-dilution OL-HDF was lower than that in pre-dilution OL-HDF (first pre- dilution: 124.8 +/- 14.3 mg/L; post-dilution: 116.6 +/- 13.9 mg/L; second pre-dilution: 125.8 +/- 13.0 mg/L; first pre-dilution vs. post-dilution, post-dilution vs. second predilution, and first pre-dilution vs. second pre-dilution: p = 0.001, p < 0.001, and p = 1.000, respectively). The most common adverse event was an increase in transmembrane pressure in the post-dilution period. Compared to pre-dilution, the postdilution method decreased the a1-microglobulin level; however, there were no significant differences in clinical symptoms or laboratory data.