Relationship between Bone Histology and Markers of Bone and Mineral Metabolism in African-American Hemodialysis Patients

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Abstract
Background and objectives: Racial differences in mineral metabolism exist in the chronic kidney disease population, especially as it relates to intact parathyroid hormone (iPTH) levels. Few data exist on the relationship of these markers to bone biopsy findings in African-American (AA) hemodialysis patients across the spectrum of renal osteodystrophy (ROD). Design, setting, participants, & measurements: In prevalent AA hemodialysis subjects, we prospectively evaluated subjects by performing transiliac bone biopsy and correlating biochemical and clinical data to bone histology. Results: Study patients (n = 43) had an average age of 53.7 (±11.6) yr, with dialysis vintage of 40.4 (±24.5) mo, 30% with diabetes, and 51% male. Bone histology revealed adynamic bone disease (ABD) (16%), mild to moderate hyperparathyroidism (HPT) (72%), severe (12%) HPT, and no osteomalacia or mixed uremic osteodystrophy. At the time of biopsy, mean corrected calcium was 9.1, 8.9, and 9.4 mg/dl (P = 0.344); calcium-phosphorus (Ca × PO4) product was 42, 55, and 62 mg2/dl2 (P = 0.002); phosphorus was 4.6, 6.2, and 6.7 mg/dl (P = 0.005); and iPTH was 225, 566, and 975 pg/ml (P = 0.006), respectively. Median values for bone-specific alkaline phosphatase (BS-AP) were 16, 34, and 64 ng/ml (P < 0.0001) among the three groups. Conclusions: These data demonstrate that across the spectrum of ROD, iPTH levels are higher than expected in AA hemodialysis subjects. iPTH, PTH peptides, and bone-specific alkaline phosphatase correlated directly with histomorphometric measurements of bone turnover and when subjects were grouped by histologic diagnosis. Only 9.5% of subjects were simultaneously within suggested Kidney Disease Outcomes Quality Initiative (K/DOQI) ranges for Ca × PO4, phosphorus, and iPTH, of which 75% demonstrated ABD on biopsy.

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