Serum phosphate levels and risk of infection in incident dialysis patients

Background and objectives: Hyperphosphatemia is highly prevalent in dialysis patients and may be associated with immune dysfunction. The association of serum phosphate level with infection remains largely unexamined. Design, setting, participants, & measurements: In an incident cohort of 1010 dialysis patients enrolled from 1995 to 1998 and treated in 80 US clinics, the association of phosphate level (low < 3.5; normal 3.5 to 5.5; high > 5.5 mg/dl) at baseline and during follow-up with the risk for incident inpatient and outpatient infection-related events was examined. Infectious events were identified from US Renal Data System data (mean follow-up 3.3 yr). Incidence rate ratios for all infections, sepsis, respiratory tract infections, and osteomyelitis were obtained using multivariable Poisson models, adjusting for potential confounders (age, race, gender, smoking, comorbidity, and laboratory values). Results: Infections of any type (n = 1398) were more frequent among patients with high phosphate levels at baseline, relative to normal; this association was not changed by adjustment for parathyroid hormone level. Similarly, high versus normal baseline phosphate was associated with increased risk for sepsis and osteomyelitis but not respiratory tract infections. Associations with calcium were generally NS, and results with calcium-phosphate product mirrored the phosphate results. Conclusions: High phosphate levels may be associated with increased risk for infection, contributing further to the rationale for aggressive management of hyperphosphatemia in dialysis patients.