Biochemical markers of bone remodeling and bone sialoprotein in ankylosingspondylitis

The aim of this work was to determine bone mineral density (BMD) in a group of patients with ankylosing spondylitis (AS) and to study alterations in b one remodeling in these patients. Eighteen patients (16 males and two femal es) with AS, mean age 44.7, range 21-75, and 18 age- and sex-matched health y controls were studied. BMD was evaluated by dual energy X-ray absorptiome try. The following biochemical markers of bone remodeling were studied: for mation - serum amino and carboxyterminal propeptides of procollagen I (PINP and PICP); resorption - urinary total and free deoxypyridinoline and pyrid inoline (TDpyr, FDpyr, TPyr and FPyr), crosslinked aminoterminal telopeptid es of collagen I (NTX), carboxyterminal telopeptide of collagen I (CTX) and serum bone sialoprotein (BSP). Receiver operatings characteristic (ROC) cu rves of markers were also performed. We found a decrease of bone mass and a n increase in TPyr, FPyr, TDpyr, FDpyr, NTX and BSP in AS, but no significa nt differences were found in PICP, PINP and CTX. FDpyr, FPyr and TPyr showe d the highest discrimination between patients and controls according to the results of the ROC curves. TPyr/TDpyr was higher in AS than in controls. W e found osteopenia, with a normal formation and a significant increase in b one resorption in AS. FDpyr, FPyr and TPyr seem to present the best sensiti vity for the study of alterations of bone resorption in this pathology, alt hough NTX, TDpyr and BSP also show significant differences. The elevation i n the ratio TPyr/TDpyr in AS compared to controls indicates that in AS ther e is a type I-collagen degradation in tissues different from bone. (C) 1999 Elsevier Science B.V. All rights reserved.