Bone alkaline phosphatase in children with chronic renal failure

Background. With the introduction of a new immunoradiometric assay based on two monoclonal antibodies (Tandem(R)-Ostase, Hybritech) the determination of bone alkaline phosphatase (BAP) to evaluate bone metabolism in chronic renal failure has become easier and more valid. Subjects and methods. Using this test we investigated BAP in a total of 90 paediatric patients, 42 (9.2 +/- 5.5 years) with chronic renal failure on conservative treatment, 22 (9.5 +/- 5.4 years) under chronic dialysis, and 26 (16.2 +/- 5.9 years) after renal transplantation, compared to 203 controls (10.1 +/- 5.7 years). Results. The physiological age dependency found in controls including two peaks during infancy and puberty was distinctly disturbed in chronic renal failure. However, in patients BAP significantly correlated with height velocity rather reflecting the last 6 (r = 0.56 P < 0.001) than the last 12 months. Although BAP correlated well with total alkaline phosphatase (TAP; r = 0.95 P < 0.001), a significant correlation with the serum level of the intact parathyroid hormone could only be detected for BAP (r = 0.45 P < 0.001) but not for TAP (r = 0.19 n.s.). Furthermore, BAP positively correlated with trabecular (n = 40; r = 0.40 P < 0.05) and inversely with cortical bone density (n = 19; r = -0.58 P < 0.01) but no relationship was found with conventional X-ray. Conclusion. BAP determined by the new radioimmunoassay seems to represent an additional diagnostic tool to assess growth and bone turnover in paediatric patients with chronic renal failure that is complementary to the information provided by X-ray and total alkaline phosphatase.