Association of calciprotein particles with serum phosphorus among patients undergoing conventional and extended-hours haemodialysis

Abstract

Background and hypothesis Extended-hours haemodialysis (HD) is associated with better clinical outcomes than conventional HD. We investigated whether extended-hours HD and conventional HD have varying effects on blood levels of calciprotein particles (CPP) and phosphorus, which have been identified as major pathogenic molecules for vascular calcification. Methods Patients who underwent conventional or extended in-centre daytime HD between January and March 2020 were included. Plasma CPP levels, representing only secondary CPP (CPP-Ⅱ), were measured in pre-dialysis samples. Linear and non-linear associations between CPP and serum phosphorus levels were examined across dialysis modalities. Results A total of 382 participants (185 undergoing extended-hours HD and 197 undergoing conventional HD) were included in the analysis. The median age of participants was 71 years, 65% of the patients were men, and the mean phosphorus level was 5.4 mg/dL. Plasma CPP (CPP-Ⅱ) levels were lower in the extended-hours HD group than in the conventional HD group (40 018 AU vs. 75 728 AU, p < 0.01). Multivariable linear regression analysis showed that extended-hours HD was associated with lower natural logarithmic plasma CPP (CPP-Ⅱ) levels: -0.64 (95% CI: -0.74 to -0.55). Restricted cubic spline function indicated that extended-hours HD was associated with lower plasma CPP (CPP-Ⅱ) levels across levels of serum phosphorus, with significant differences observed between groups, especially in hyperphosphatemic conditions (P for interaction < 0.01). Conclusions The extended-hours HD group had lower CPP levels than the conventional HD group despite no significant differences in serum phosphorus levels, which may contribute to better clinical outcomes in patients on extended-hours HD.