Serum Levels of Intact Parathyroid Hormone, Calcium, and Phosphorus and Risk of Mortality in Hemodialysis Patients

Background: Abnormal mineral metabolism is common among hemodialysis patients and has been associated with higher morbidity and mortality rates. Methods: A cohort of 532 hemodialysis patients was selected from nine hemodialysis centers in September 2012 and were prospectively followed-up for a median of 28 months. Unadjusted and adjusted (in terms of age, gender, dialysis vintage, body mass index, albumin level, and comorbidities) hazard ratios (HRs) of mortality associated with serum phosphorus, calcium, and parathyroid hormone (PTH) levels were calculated, using Cox proportional hazards model. Results: In the unadjusted model, HRs of mortality for serum phosphorus < 4 mg/dL (reference: 4 - 6) and iPTH < 200 pg/mL (reference: 200 - 600) were 1.61 (95% CI: 1 - 2.46) and 1.55 (95% CI: 1.06 - 2.27), respectively. After adjustment, the foregoing values were no longer significant, and HRs for serum phosphorus level ≥ 6 mg/dL (reference: 4 - 6), calcium level ≥ 10 (reference: < 10), and iPTH ≥ 600 (reference: 200 - 600) were calculated to be 1.56 (95% CI: 1.09 - 2.22), 2.34 (95% CI: 1.21 - 4.51), and 1.59 (95% CI: 1.03-2.45), respectively. Meanwhile, significant adjusted correlates of iPTH were serum alkaline phosphatase (r = 0.49), phosphorus (r=0.24), dialysis vintage (r = 0.21), age (r = -0.20), diabetes (r = -0.16), and serum calcium level (r = -0.13). Conclusions: While high serum PTH, calcium, and phosphorus levels could determine the mortality risk in hemodialysis patients, decreased serum phosphorus and PTH levels were in association with malnutrition and comorbidities and were not independent risk factors for mortality.