Effect Modifying Role of Serum Calcium on Mortality-Predictability of PTH and Alkaline Phosphatase in Hemodialysis Patients: An Investigation Using Data from the Taiwan Renal Registry Data System from 2005 to 2012

Abstract

Predicting mortality in dialysis patients based on low intact parathyroid hormone levels is difficult, because aluminum intoxication, malnutrition, older age, race, diabetes, or peritoneal dialysis may influence these levels. We investigated the clinical implications of low parathyroid hormone levels in relation to the mortality of dialysis patients using sensitive, stratified, and adjusted models and a nationwide dialysis database. We analyzed data from 2005 to 2012 that were held on the Taiwan Renal Registry Data System, and 94,983 hemodialysis patients with valid data regarding their intact parathyroid levels were included in this study. The patient cohort was subdivided based on the intact parathyroid hormone and alkaline phosphatase levels. The mean hemodialysis duration within this cohort was 3.5 years. The mean (standard deviation) age was 62 (14) years. After adjusting for age, sex, diabetes, the hemodialysis duration, serum albumin levels, hematocrit levels, calcium levels, phosphate levels, and the hemodialysis treatment adequacy score, the single-pool Kt/V, the crude and adjusted all-cause mortality rates increased when alkaline phosphatase levels were higher or intact parathyroid hormone levels were lower. In general, at any given level of serum calcium or phosphate, patients with low intact parathyroid hormone levels had higher mortality rates than those with normal or high iPTH levels. At a given alkaline phosphatase level, the hazard ratio for all-cause mortality was 1.33 (p < 0.01, 95% confidence interval 1.27–1.39) in the group with intact parathyroid hormone levels < 150 pg/mL and serum calcium levels > 9.5 mg/dL, but in the group with intact parathyroid hormone levels > 300 pg/mL and serum calcium levels > 9.5 mg/dL, the hazard ratio was 0.92 (95% confidence interval 0.85–1.01). Hence, maintaining albumin-corrected high serum calcium levels at > 9.5 mg/dL may correlate with poor prognoses for patients with low intact parathyroid hormone levels.

Variability in Predialysis Systolic Blood Pressure and Long-Term Outcomes in Hemodialysis Patients

“…This finding deserves special consideration given the high incidence of chronic kidney disease-mineral and bone disorder (CKD-MBD) and the widespread use of calcium-based binders in hemodialysis patients. A growing number of studied have demonstrated that higher calcium levels are associated with higher mortality [31, 32]. It is possible that the impact of calcium levels on BPV is a mechanism underlying this relationship.…”

Association between Extreme Values of Markers of Chronic Kidney Disease: Mineral and Bone Disorder and 5-Year Mortality among Prevalent Hemodialysis Patients

“…Previous studies have reported that iPTH levels and the risk of death in HD patients show a J-curve relationship [4,13,14,15]. Recently, data from the Taiwan Renal Registry Data System showed that at any level of serum Ca or P, patients with low iPTH levels had higher mortality rates than those with normal or high iPTH levels [16]. However, some reports also found no association between low iPTH levels and mortality in HD patients [1,2,4,19,20,21].…”

“…In general, patients with CKD who had higher levels of serum Ca, P, and iPTH were at an increased risk for death [3,4,13,14,15]. In contrast, a few reports demonstrated that low iPTH levels increase the mortality risk in patients with CKD [4,15,16]. Possible reasons for these variations in results among previous studies are (1) non-uniform management protocols in cohort studies, (2) variations in study participant demographics, and (3) difference in the statistical methods used.…”

Relationship between serum calcium level at dialysis initiation and subsequent prognosis

“…In patients on dialysis, serum phosphorus levels have been shown to have a U-shaped association with mortality [2][3][4][5][6][7]. As for serum calcium levels, although it is not clear whether low levels are detrimental, high levels are known to be associated with a poor prognosis [3,4,8]. Given these background conditions, each guideline provides target values for serum phosphorus and calcium levels when managing patients on dialysis [1,9].…”