Impact of race on hyperparathyroidism, mineral disarrays, administered vitamin D mimetic, and survival in hemodialysis patients

Abstract

Blacks have high rates of chronic kidney disease, are overrepresented among the US dialysis patients, have higher parathyroid hormone levels, but greater survival compared to nonblacks. We hypothesized that mineral and bone disorders (MBDs) have a bearing on survival advantages of black hemodialysis patients. In 139,328 thrice-weekly treated hemodialysis patients, including 32% blacks, in a large dialysis organization, where most laboratory values were measured monthly for up to 60 months (July 2001 to June 2006), we examined differences across races in measures of MBDs and survival predictabilities of these markers and administered the active vitamin D medication paricalcitol. Across each age increment, blacks had higher serum calcium and parathyroid hormone (PTH) levels and almost the same serum phosphorus and alkaline phosphatase levels and were more likely to receive injectable active vitamin D in the dialysis clinic, mostly paricalcitol, at higher doses than nonblacks. Racial differences existed in mortality predictabilities of different ranges of serum calcium, phosphorus, and PTH but not alkaline phosphatase. Blacks who received the highest dose of paricalcitol (>10 µg/week) had a demonstrable survival advantage over nonblacks (case-mix-adjusted death hazard ratio = 0.87, 95% confidence level 0.83-0.91) compared with those who received lower doses (<10 µg/week) or no active vitamin D. Hence, in black hemodialysis patients, hyperparathyroidism and hypercalcemia are more prevalent than in nonblacks, whereas hyperphosphatemia or hyperphosphatasemia are not. Survival advantages of blacks appear restricted to those receiving higher doses of active vitamin D. Examining the effect of MBD modulation on racial survival disparities of hemodialysis patients is warranted.

Fig. 1

Comparing 3-month average serum calcium (left panel) and phosphorus (right panel) concentrations in the base calendar quarter across eight 10-year age increments in 139,328 hemodialysis patients including 43,974 African Americans (32%) and 95,354 non-African Americans (68%) from July 2001 to June 2001.

Fig. 2

Comparing 3-month average serum intact PTH (left panel) and alkaline phosphatase (right panel) concentrations in the base calendar quarter across eight 10-year age increments in 139,328 hemodialysis patients including 43,974 African Americans (32%) and 95,354 non-African Americans (68%) from July 2001 to June 2001.

Fig. 3

Pattern of active vitamin D administration in the examined calendar quarters across eight 10-year age increments in 139,328 hemodialysis patients from July 2001 to June 2001. (Left panel) Proportion of hemodialysis patients who received any dose of an active vitamin D compound (paricalcitol 58%, calcitriol 2%, doxercalciferol <1%, and no active vitamin D 38%) in 43,974 African-American and 95,354 non-African-American hemodialysis patients. (Right panel) The 3-month average administered paricalcitol dose (mean ± SD) among 49,674 hemodialysis patients (including 19,918 African Americans) who received any dose of paricalcitol during the calendar quarter.

Fig. 4

Death hazard ratios (and 95% confidence intervals) of 5-year average corrected albumin-adjusted serum calcium levels in 139,328 hemodialysis patients including 43,974 African Americans (32%) and 95,354 non-African Americans (68%) from July 2001 to June 2001 across four a priori selected increments of serum calcium (left panel) and phosphorus (right panel) concentrations. Reference group in each analysis is African-American hemodialysis patient population with a KDOQI-recommended target range, that is, calcium level 8.4 to 9.5 mg/dL and phosphorus level 3.5 to 5.5 mg/dL, respectively.

Fig. 5

Death hazard ratios (and 95% confidence intervals) of 5-year average corrected albumin-adjusted serum calcium levels in 139,328 hemodialysis patients including 43,974 African Americans (32%) and 95,354 non-African Americans (68%) from July 2001 to June 2001 across four a priori selected increments of serum intact PTH (left panel) and alkaline phosphatase (right panel) concentrations. Reference group in each analysis is African-American hemodialysis patient population with a recommended target range, that is PTH 150 to 300 pg/mL and alkaline phosphatase 80 to 120 U/L, respectively.

Fig. 6

Death hazard ratios of African-American (AA) versus non-AA patients across three mutually exclusive strata of no active vitamin D (n = 18,981, right section), low paricalcitol dose (>0 and <10 µg/week, n = 17,347, middle section) and high paricalcitol dose (≥10 µg/week, n = 32,327, left section). Survival analyses were performed in unadjusted and case-mix-adjusted formats (see text for list of covariates).