Serum bioactive parathyroid hormone in hemodialysis patients.

In 41 hemodialysis patients with bone disease (histological diagnosis with histomorphometric confirmation of PTH activity) results from a serum immunoreactive PTH (iPTH) assay correlated with results from a new serum bioactive PTH (bio-PTH) assay (r = 0.84; P less than 0.001). The serum bio-PTH values correlated well with osteoclast numbers (r = 0.70; P less than 0.001), resorption surfaces (r = 0.55; P less than 0.001), and presence of marrow fibrosis (P less than 0.02). The serum iPTH values also correlated with osteoclast numbers (r = 0.61; P less than 0.001), resorption surfaces (r = 0.47; P less than 0.003), and presence of marrow fibrosis (P less than 0.02). Serum bio-PTH and iPTH values were higher in patients with severe hyperparathyroidism than in other patients. The assays were equally useful in identifying dialysis patients with severe hyperparathyroidism. Patients with osteomalacia or low turnover bone disease had low serum bio-PTH and/or iPTH values. Low bio-PTH values (less than or equal to 3.6 pmol/L) had a sensitivity and a specificity of 93% for osteomalacia or low turnover bone disease. Low bio-PTH values also were useful in identifying those patients with positive aluminum staining in bone. The serum bio-PTH assay was useful in identifying patients with osteomalacia, low turnover bone disease, or aluminum accumulation.