Relationship between alkaline phosphatase and all-cause mortality in peritoneal dialysis patients

Elevated levels of serum alkaline phosphatase (AlkPhos) have been reported to be associated with increased mortality risk in hemodialysis (HD) patients. We examined the association of serum AlkPhos with all-cause mortality in our PD patients. The study enrolled 90 PD patients beginning in 1995. On enrollment, demographics and clinical and biochemical data were recorded. Patients were followed to September 2011. Mean age of the enrollees was 52 years, with 61% being women, and most (81%) being of African descent. Mean and median AlkPhos were 135 U/L and 113 U/L respectively. Mean and maximum follow-up were 2.61 and 16 years respectively. As expected, AlkPhos correlated directly with serum intact parathyroid hormone (r = 0.36, p = 0.003). In a Cox multivariate regression analysis with adjustment for confounding variables, AlkPhos as a continuous (relative risk: 1.016; p = 0.004) anda categorical variable [> 120 U/L and < or = 120 U/L (relative risk: 6.0; p = 0.03)] remained a significant independent predictor of mortality. For each unit increase in enrollment AlkPhos, there was a 1.6% increase in the relative risk of death. Elevated serum AlkPhos is significantly and independently associated with increased mortality risk in our PD patients followed for up to 16 years. AlkPhos should be evaluated prospectively as a potential therapeutic target in clinical practice.