Magnitude and impact of abnormal mineral metabolism in hemodialysis patients in the Dialysis Outcomes and Practice Patterns Study (DOPPS).

BACKGROUND

Mineral metabolism has emerged as an important predictor of morbidity and mortality in dialysis patients, independent of bone and muscle concerns. Several expert panels have issued management guidelines for mineral metabolism.

METHODS

The state of mineral metabolism (serum parathyroid hormone [PTH], phosphorus, calcium, and calcium-phosphorus product) was described for representative samples of patients and facilities from 7 countries (France, Germany, Italy, Japan, Spain, United Kingdom, and United States) participating in the Dialysis Outcomes and Practice Patterns Study (DOPPS I, 1996-2001; DOPPS II, 2002-2004).

RESULTS

A relatively modest percentage of patients fell within the guideline range for PTH (21.4% in DOPPS I, 26.2% in DOPPS II), serum phosphorus (40.8%, 44.4%), albumin-corrected serum calcium (40.5%, 42.5%), and calcium-phosphorus product (56.6%, 61.4%). Results were not dramatically different across countries. The majority of patients not within guideline ranges had high serum levels of phosphorus (51.6% in DOPPS I, 46.7% in DOPPS II), calcium (50.1%, 48.6%), and calcium-phosphorus product (43.4%, 38.6%) and low (<150 pg/mL) concentrations of PTH (52.9%, 47.5%). It was rare for patients to fall within recommended ranges for all indicators of mineral metabolism; 23% to 28% fell within guideline for at least 3 measures and only 4.6% to 5.5% of patients were within range for all 4. The risks of all-cause and cardiovascular mortality were directly and independently associated with each of the 4 indicators.

CONCLUSION

The DOPPS provides a useful comparison benchmark for the state of mineral metabolism management of patients with kidney disease; it also affirms the association between mineral metabolism and important patient outcomes.