Abnormal Mineral, Bone Markers in Dialysis Patients Hike Mortality

Large European study identifies ranges of phosphorus, calcium, and parathyroid hormone levels with the lowest death risk.
Large European study identifies ranges of phosphorus, calcium, and parathyroid hormone levels with the lowest death risk.

Abnormalities in mineral and bone metabolism markers are associated with worse survival in the adult hemodialysis population, according to a new study.

Researchers who analyzed data from 6,307 randomly selected adult HD patients from 20 European countries who participated in COSMOS, a 3-year multicenter prospective study, found that both high and low serum phosphorus, calcium, and parathyroid hormone (PTH) were associated with a higher risk of mortality.

In addition, results showed that serum values associated with the minimum relative risk of death were 4.4 mg/dL for serum phosphorus, 8.8 mg/dL for serum calcium, and 398 pg/mL for serum PTH, investigators led by Jorge B. Cannata-Andia, MD, of Universidad de Oviedeo, Oviedeo, Asturias, Spain, and colleagues reported online ahead of print in Nephrology Dialysis Transplantation. Using these values as a base, the lowest mortality risk ranges were 3.6–5.2 mg/dL for serum phosphorus, 7.9–9.5 mg/dL for serum calcium, and 168–674 pg/mL for serum PTH. Decreases in serum phosphorus and calcium and increases in serum PTH in patients with baseline values greater than 5.2 mg/dL for phosphorus, greater than 9.5 mg/dL for calcium, and less than 168 pg/mL for PTH, respectively, were associated with improved survival.

Compared with a serum phosphorus level of 3.6–5.2 mg/dL, levels less than 3.6 and greater than 5.2 mg/dL were associated with a 34% and 34% increased relatively risk of death, respectively, in a fully adjusted model. Compared with a serum calcium level of 7.9–9.5 mg/dL, levels less than 7.9 and greater than 9.5 mg/dL were associated with a 13% and 32% increased relative risk of death, respectively. Compared with a serum PTH level of 168–674 pg/mL, levels less than 168 and greater than 674 were associated with a 17% and 39% increased relative risk of death, respectively.

The authors propose the serum value ranges found in COSMOS as a complement or alternative to the existing ranges set forth in the Kidney Disease Outcomes Quality Initiative (KDOQI) and Kidney Disease: Improving Global Outcomes (KDIGO) clinical guidelines.

“One of the most attractive and practical contributions of this new data from COSMOS is related to the strategy used to find the lowest mortality risk ranges for serum phosphorus, calcium and PTH, which differs from previous studies,” the authors wrote.

Dr. Cannata-Andia and his colleagues acknowledged that the study was limited by its observational nature, so determinations about causality cannot be made.

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