BONE ALKALINE-PHOSPHATASE ISOENZYME IN RENAL OSTEODYSTROPHY

Serum total alkaline phosphatase is the most commonly used biochemical marker of bone disease in renal patients, but alkaline phosphatase or iginates from different organs and sometimes lacks specificity. Bone i soenzyme measurement is considered superior to total alkaline phosphat ase for the assessment of bone metabolism. We have studied the value o f bone isoenzyme, determined by a new IRMA (Tandem-R-Ostase), in haemo dialysis patients with secondary hyperparathyroidism and renal osteody strophy. Fifty-six haemodialysis patients were studied. Intact parathy roid hormone (PTH), osteocalcin, total alkaline phosphatase and bone a lkaline phosphatase were determined. A transiliac bone biopsy was perf ormed in 20 of the 56 patients after double tetracycline labelling. Th ere was a significant correlation between bone alkaline phosphatase an d PTH (r=0.79, P<0.001) and between bone and total alkaline phosphatas e (r=0.84, P<0.001) in all patients. The patients who underwent a bone biopsy showed osteitis fibrosa in 17, mixed lesion in one, adynamic b one disease in one and normal bone in one. Bone alkaline phosphatase s howed a significant correlation with static and dynamic histomorphomet ric indices similar to that obtained with PTH and better than those of total alkaline phosphatase and osteocalcin. It is concluded that bone alkaline phosphatase (ostase) seems to be a useful non-invasive marke r of bone metabolism in patients on haemodialysis with high turnover b one disease. More studies are necessary to know its value in low turno ver bone disease.