Biological Variability of Serum Immunoreactive Bone Sialoprotein

摘要

Serum immunoreactive bone sialoprotein (sBSP) accounts for approx. 10% of the non-collagenous proteins of bone. Recent findings suggest that its serum concentrations reflect processes linked to osteoclast activity and bone resorption. In order to determine the biological and technical variability of serum BSP, the following studies have been performed: ⅰ) measurements of serum BSP in different genders and age groups in healthy subjects (n = 290); ⅱ) day-to-day variation (n = 9); and ⅲ) diurnal variation (n = 10). Serum BSP values were quantified using a newly developed polyclonal RIA for human BSP. Serum BSP levels were significantly higher in children and adolescents, with highest values during early childhood and during puberty. In women, a 50% rise in serum BSP levels was found after the menopause. Day-to-day variability ranged between 7.3 and 17.7% (mean: 11.7%). Diurnal variation showed a peak between 04:00 and 08:00 a.m., followed by a steady decline until noon. The maximum amplitude of this diurnal change was approx. ± 20% (mean BSP concentration 10.5 ng/mL). In conclusion, serum BSP concentrations indicate increased bone turnover soon after the menopause, reflect the pubertal growth spurt, show little day-to-day variability, and exhibit significant diurnal variation.