An update on biomarkers of bone turnover and their utility in biomedical research and clinical practice

New Automated Multiplex Assay for Bone Turnover Markers in Osteoporosis

Background: Serum C-terminal cross-linked telopeptide of type I collagen (CTX-I), N-terminal propeptide of type I collagen (PINP), and osteocalcin (OC) are among the most sensitive bone turnover markers for evaluating osteoporosis. Each marker is currently measured individually by manual or automated immunoassays that are time consuming and require substantial sample volume. We evaluated the performance characteristics of a novel, fully automated, protein-array chip system that allows the simultaneous measurement of CTX-I, PINP, OC, and intact parathyroid hormone (PTH) in 20 μL of serum.

Methods: We measured CTX-I, PINP, OC, and PTH using multiplex and corresponding automated single assays in 157 healthy premenopausal women, 74 healthy men, and 56 postmenopausal osteoporotic women before and 6 months after treatment with oral ibandronate (150 mg/month).

Results: Within- and between-run CVs of the multiplex assay were similar to those of single measurement assays (<10% for all markers), whereas the limit of quantification was lower, except for OC. Multiplex values highly correlated (r > 0.93, P < 0.0001 for all markers) with the corresponding single assays, and measured concentrations were comparable. After 6 months of ibandronate, CTX-I, PINP, and OC decreased by a median of 48%, 63%, and 52%, respectively (P < 0.0001 for all 3 markers), magnitudes similar to those of the corresponding single assays.

Conclusions: The automated protein-array chip demonstrated similar analytical precision, improved analytical sensitivity, and comparable measured concentrations to those of single assays. The multiplex assay should be useful for assessing bone metabolism in large clinical studies, particularly when sample volume is limited.

[Biochemical bone resorption markers during the healing of osteoporotic fractures]

BACKGROUND

This study investigated the progression and clinical relevance of biochemical resorption marker values during fracture healing in osteoporosis.

PATIENTS AND METHODS

In 44 patients with distal radius fractures and 29 patients without fractures, the blood and urine concentrations of pyridinoline (PYD), deoxypyridinoline (DPD), N-telopeptides (NTx), and bone sialoprotein (BSP) were recorded on the day of trauma as well as during further progression. All postmenopausal patients underwent bone density measurement. Accordingly, patients were divided into premenopausal, postmenopausal osteoporotic, and postmenopausal nonosteoporotic groups.

RESULTS

Between the groups, PYD, DPD, and NTx showed significant differences in their initial values. However, their further relative progression was primarily affected by the chosen therapy.

CONCLUSION

Bone resorption markers can diagnostically point to osteoporosis and are significant parameters in fracture healing.

Rapid suppression of bone resorption marker levels with ibandronate therapy in a bisphosphonate-naïve population

This 6-mo open-label study assessed the pattern of bone turnover marker (BTM) level changes in bisphosphonate-naïve women with postmenopausal osteoporosis treated with monthly oral ibandronate 150mg and the correlation between month 1 and month 6 serum C-terminal cross-linking telopeptide of type I collagen (sCTX) levels. The following BTMs were monitored: sCTX, urinary N-terminal telopeptide of type I collagen (uNTX), serum procollagen type 1 N-terminal propeptide (PINP), serum osteocalcin (OC), and serum bone-specific alkaline phosphatase (bALP). BTM levels were measured immediately before dosing at baseline and months 1, 2, 3, and 6, and 7d after dosing at baseline and month 4. A multiple regression model was applied to determine whether month 1 sCTX response predicted month 6 sCTX change. sCTX levels declined 70% 7d after dosing at baseline and month 4. Predosing sCTX declined 55% at month 6. The pattern of uNTX reduction was similar to sCTX. Bone formation markers PINP, OC, and bALP declined gradually over time. Month 1 sCTX change was a significant predictor of Month 6 change (p=0.0001). Once monthly 150mg oral ibandronate treatment reduced BTMs in women with osteoporosis. sCTX reduction occurred within 7d and was sustained over 6mo. Month 1 sCTX predicted month 6 sCTX.

Quarterly intravenous ibandronate for postmenopausal osteoporosis

Osteoporosis is under-recognized and undertreated among postmenopausal women. Nitrogen-containing bisphosphonates are its first-line pharmacotherapy. Oral bisphosphonate treatment requires stringent dosing guidelines to minimize gastrointestinal irritation and enhance absorption. This paper reviews the efficacy, safety and tolerability of quarterly intravenous ibandronate 3 mg injection, approved in 2006 in the USA and Europe. Quarterly intravenous ibandronate injection has shown superior efficacy to daily oral ibandronate for bone mineral density increase and fracture prevention. No drug-related serious atrial fibrillation events have been reported with intravenous ibandronate. The regimen has a favorable renal safety profile. Quarterly intravenous ibandronate is administered as a simple 15-30-s intravenous injection in a physician's office and provides a beneficial option for patients who are unable to tolerate oral administration.