Towards optimising the provision of laboratory services for bone turnover markers

Bone turnover markers (BTMs) are either secreted by osteoblasts during bone formation or released by degradation of the collagen matrix of bone during bone resorption, and may be measured in blood or urine to provide an estimate of the rate of bone remodelling. Increased bone remodelling rate is often associated with bone loss which can result in osteoporosis; however, lack of data preclude the inclusion of BTMs in fracture risk algorithms. The changes in BTMs following therapy for osteoporosis may be useful for monitoring. Serum procollagen type I amino-terminal propeptide (s-PINP) and serum carboxy-terminal cross-linking telopeptide of type I collagen (s-βCTX) have been designated as reference standard markers of bone formation and resorption respectively in osteoporosis; further research is needed for their routine use in osteoporosis. BTMs are useful in diagnosing and monitoring Paget's disease of bone and other bone diseases associated with abnormal bone formation and/or resorption. Standardised patient preparation is required to mitigate the effect of biological variation, and appropriate sample handling and storage are important to minimise sample degradation. Significant inter-method differences exist for BTMs, and harmonisation of methods for the reference BTMs is being pursued. This will help develop universally accepted decision limits and treatment goals. Australian consensus reference intervals have been developed for some methods for s-PINP and s-βCTX.