Bone alkaline phosphatase isoenzyme in renal osteodystrophy

Area of Science:

• Nephrology
• Biochemistry
• Bone Metabolism

Background:

• Serum total alkaline phosphatase lacks specificity for bone disease in renal patients.
• Bone isoenzyme measurement offers superior assessment of bone metabolism compared to total alkaline phosphatase.
• Secondary hyperparathyroidism and renal osteodystrophy are common in hemodialysis patients.

Purpose of the Study:

• To evaluate the utility of a new bone isoenzyme assay (Tandem-R-Ostase) in hemodialysis patients.
• To correlate bone alkaline phosphatase levels with intact parathyroid hormone (PTH), osteocalcin, and bone biopsy findings.
• To assess bone alkaline phosphatase as a non-invasive marker for bone disease in renal patients.

Main Methods:

• Studied 56 hemodialysis patients.
• Measured intact parathyroid hormone (PTH), osteocalcin, total alkaline phosphatase, and bone alkaline phosphatase.
• Performed transiliac bone biopsy with double tetracycline labeling in 20 patients.

Main Results:

• Bone alkaline phosphatase significantly correlated with PTH (r=0.79) and total alkaline phosphatase (r=0.84).
• Bone biopsy revealed high turnover bone disease (osteitis fibrosa) in 17 patients.
• Bone alkaline phosphatase showed significant correlations with static and dynamic histomorphometric indices, outperforming total alkaline phosphatase and osteocalcin.

Conclusions:

• Bone alkaline phosphatase (Ostase) is a useful non-invasive marker for high turnover bone disease in hemodialysis patients.
• Further research is needed to determine its value in low turnover bone disease.
• Bone isoenzyme measurement provides a more specific assessment of bone metabolism in renal patients.