The Role of Kt/V and Creatinine clearance on Assisting Optimization of Serum Phosphorus Levels among Patients on PD.

Abstract

Background: Hyperphosphatemia is associated with poor outcome and is still very common in peritoneal dialysis (PD) patients. Since peritoneal phosphate clearance is closer to peritoneal creatinine clearance than urea clearance, we hypothesized that weekly creatinine clearance (CrCl) could be a better marker of serum phosphate in PD.

Methods: In a retrospective observational study, data from adult PD patients were collected across five institutions in North and South America: LATAM, RRI, Mount Sinai Hospital, Hospital Civil de Guadalajara, and the BRAZPD cohort. All centers analyzed routinely available laboratory data, with exclusions for missing data on serum phosphate, CrCl, or urea Kt/V. A unified statistical protocol was employed across centers. Linear mixed-effect models examined associations between longitudinal serum phosphate levels, CrCl, and Kt/V. Adjustments were made for age, gender, and baseline phosphate binder usage. Mixed-effects meta-analysis determined the pooled effect size of CrCl and Kt/V on serum phosphate trajectories, adjusted for confounders.

Results: There were 16,796 incident PD patients analyzed. Age, BMI, gender, PD modality, Kt/V and CrCl as well as serum phosphate varied significantly across the different cohorts, but >70% had residual renal function. For most cohorts, both CrCltotal and urea Kt/V associated negatively with serum phosphorus levels, and log-likelihood ratio tests demonstrate that models including CrCltotal have more predictive information than those including only urea Kt/V for the largest cohorts. Models including CrCltotal increase information predicting longitudinal serum phosphate levels irrespective of baseline urea Kt/V, age, use of phosphorus binder, and gender.

Conclusions: CrCl was not more accurate in predicting serum phosphate than urea Kt/V, but its inclusion in multivariable models predicting serum phosphate added accuracy. In conclusion, both creatinine clearance and Kt/V are associated with phosphate levels, and using both biomarkers, instead of just one, may better assist in the optimization of serum phosphate levels.