Abstract: TH-PO1040

Phosphate and Phosphate Changes Are Associated with Mortality in Dutch Dialysis Patients: A Registry Based Analysis

Session Information

Category: Mineral Disease

  • 1201 Mineral Disease: Ca/Mg/PO4

Authors

  • Hoekstra, Tiny, VU University Medical Center, Amsterdam, Netherlands
  • van Ittersum, Frans J., VU University Medical Center, Amsterdam, Netherlands
  • Hemmelder, Marc H., Nefrovisie Foundation, Utrecht, Netherlands
  • Vervloet, Marc G., VU University Medical Center, Amsterdam, Netherlands
Background

Observational data suggest that an improvement over time of hyperphosphatemia in dialysis patients is associated with improved mortality. However it is unknown if an absolute or relative decline is optimal. This knowledge could have clinical implications. Our aim is to associate the magnitude of changes in phosphate concentration with survival taking into account its initial value.

Methods

At quarterly intervals data on phosphate are available in a subset (N=5,487) of the Dutch renal replacement registry. Patients were followed from the date of the first available measurement until death or censoring (transplantation, recovery of renal function, lost to follow-up, end of study period). Time-updated cox regression analysis was performed with phosphate as well as changes in phosphate between subsequent measurements as continuous exposure variables. To allow for non-linear associations penalized splines smoothing was used. The analyses with changes were also performed stratified for categories of initial phosphate level. Adjustments were performed for age, sex, primary kidney disease, vintage, year of baseline, dialysis modality, previous transplantation.

Results

Both phosphate levels and phosphate changes showed a non-linear, U-shaped association with mortality. Lowest mortality was found for phosphate levels around 1.25 mmol/L. A gradually increase in benefit of phosphate decrease was observed across strata of initial phosphate level (from < 1.5 mmol/L to > 2.00 mmol/L), suggesting that a phosphate target of about 1.40 mmol/L is optimal. (Figure 1).

Conclusion

Patients with higher baseline phosphate concentrations appear to benefit form a greater absolute decline. Our data reinforce current clinical practice aiming at a target range for dialysis patients with hyperphosphatemia, instead of a fixed absolute decline.