The diagnostic and predictive value of serum intact parathyroid hormone (iPTH) and osteocalcin (bone Gla protein, BGP), alone or in combination, have been examined in only a small number of haemodialysis patients.
Methods: We studied prospectively 114 patients (46 women, 68 men; mean age 52 +/- 12 years) on regular haemodialysis for a mean of 55 (6-185) months. All patients underwent labelled transiliac bone biopsy, and serum levels of iPTH, BGP and alkaline phosphatase were determined.
Results: Seventy-one patients (62%) showed histological findings of hyperparathyroid bone disease, 24 (21%) mixed bone disease, six (5.5%) osteomalacia and 13 (11.5%) adynamic bone. Bone aluminium deposition over more than 25% of the trabecular bone interface was found in 66 patients (58%). Serum iPTH and BGP correlated with the majority of histomorphometric indices of bone formation, mineralization and resorption (r > 0.5, P < 0.01). iPTH levels > or = 200 pg/ml and BGP > or = 50 ng/ml were found to be indicative of hyperparathyroid bone disease, whilst iPTH levels < 65 pg/ml and BGP < 20 ng/ml were indicative of adynamic bone. However, the positive predictive value of these indices was limited (less than 80%), although their negative predictive value, especially when used in combination, was good (more than 90%) and the exclusion of hyperparathyroid bone disease and adynamic bone was possible. The diagnostic and predictive value of these bone markers were improved when patients with bone aluminium deposition were excluded.
Conclusions: Diagnosis of hyperparathyroid bone disease and adynamic bone is difficult on the basis of iPTH and BGP, especially when bone aluminium deposition is prevalent. However, using these bone markers, preferably in combination, the exclusion of these lesions is feasible.