Novel serum markers of bone resorption: Clinical assessment and comparisonwith established urinary indices

Although urinary measurements of collagen degradation provide valid estimat es of bone resorption, their clinical application is hampered by pronounced analytical and biological variability. Therefore, immunoassays for the det ermination of such parameters in serum have been developed. In this study, we assessed the performance of three new serum markers of bone turnover, i. e., C-terminal and N-terminal telopeptides of type I collagen (S-CTX and S- NTX) and bone sialoprotein. Results were compared with urinary total pyridi noline, total deoxypyridinoline, and urinary C-terminal telopeptides of typ e I collagen (U-CTX) and urinary N-terminal telopeptides of type I collagen (U-NTX). The study population included healthy men (n = 27), premenopausal (n = 30) and postmenopausal (n = 31) women, patients with hepatic dysfunct ion (HF, n = 24), renal failure (RF, n = 30), breast cancer without (BC-, n = 24) and with (BC+, n = 30) bone metastases, primary vertebral osteoporos is (OPO, n = 27), primary hyperparathyroidism (PHPT, n = 16), active Paget' s disease of bone (n = 18), multiple myeloma (MM, n = 18), and patients wit h hypercalcemia of malignancy before and after treatment with pamidronate ( HOM, n = 28). Changes in urinary and serum markers were similar in most met abolic bone diseases. However, differentiation between healthy controls and OPO, or PHPT, was improved by the serum markers. In MM, all serum and urin ary markers were elevated (p < 0.05 vs. controls). In BC+,skeletal involvem ent was reflected by significant increments in all indices (p < 0.01 vs. BC -), except U-CTX and S-CTX. In HOM, pamidronate-induced changes in biomarke rs were most pronounced for U-CTX and S-CTX and S-NTX. HF and RF were assoc iated with elevated levels of all serum markers (p < 0.05 vs, controls). In conclusion, measurements in serum reflect bone resorption to the same exte nt as the urinary indices. Since serum markers circumvent some of the limit ations of urinary measurements, their use potentially improves the assessme nt of skeletal disorders.