FC 115HIGHER VARIABILITY OF SERUM PHOSPHATE IS ASSOCIATED WITH INCREASED MORTALITY RISK ONLY WHEN ASSOCIATED WITH HYPOALBUMINEMIA

Abstract

Abstract Background and Aims Both hypophosphatemia and hypoalbuminemia are established risk factors for mortality in hemodialysis (HD) patients. Evidence indicates that higher variability of serum phosphate (P) is associated with higher risk of mortality. However, little is known about to what extent of this association is influenced by other risk factors, most importantly nutritional or inflammatory state. The aim of this study was to analyze the variability of serum P with all-cause mortality taking into account the interaction with the levels of albumin (Alb) Method All adult incident HD patients treated in Fresenius Medical Care North America (FMCNA) clinics between 01/2010 and 10/2018 were included. Serum P and Alb levels were averaged from month 1 to 6 after the start of dialysis (baseline). Baseline variability of P was described by coefficient of variation (CV). All-cause mortality was recorded between months 7 and 18. Cox proportional hazards models with spline terms were applied to explore the association between variability of P and Alb and all-cause mortality. Additionally, tensor product smoothing splines were computed to study the interactions of Alb and P variability and their associations with outcomes respectively. Results We enrolled 353,142 patients. The average age was 62.7 years, 58% were male, 64% were diabetic. Baseline P was 4.98 mg/dL, median serum P CV was 0.19. Baseline Alb was 3.61 g/dL. While we studied the joint effect of P variability with Alb on outcome, the association between P variability and outcomes appeared to be predominant in patients with low serum Alb levels (Fig. 1). Conclusion Higher P variability is associated with adverse outcomes but predominantly in patients with hypoalbuminemia. This suggests a major role for malnutrition and/or inflammation as explanatory factors for the association between P variability in outcome. A high P variability in this patient group can be interpreted as an additional risk factor. When studying the relation between the variability of a single parameter with outcome, the possible underlying role of “third factors” should be explored, for which the methodology used in this abstract might provide an example.