Bone Marker - NTX
Biochemistry Overview / Directory
Purpose of the test
Human bone is continuously remodelled through a coupled process of bone resorption by osteoclasts followed by bone formation by osteoblasts. This process is necessary for normal development and maintenance of the skeleton. Abnormalities in this tightly coupled process often results in changes in skeletal mass and shape. The measurement of specific degradation products of bone matrix provides information on the rate of bone turnover.
Approximately 90% of the organic matrix of bone tissue is type I collagen. Type I collagen, a helical protein that is cross-linked at the N-terminal and C-terminal ends of the molecule, forms the basic fabric and tensile strength of bone tissue. Hydroxylysylpyridinoline and lysylpyridinoline are the predominant cross-linking amino acids of bone collagen. Total pyridinoline cross-links are excreted in urine in free and peptide bound forms and have been utilised for research of bone resorption by HPLC techniques. The discovery of urinary cross-linked N-telopeptides of type I collagen (NTx) has provided a specific biochemical marker of human bone resorption which can be analysed by immunoassay. The NTx molecule is specific to bone due to the unique aminoacid sequence and orientation of the cross-linking alpha-2 N-telopeptide. Generation of the NTx molecule is mediated by osteoclasts in bone and the urine concentration is directly related to the extent of bone resorption. Research has demonstrated that elevated bone resorption is the primary cause of age-related bone loss and that low bone mass often results in osteopenia and is the major cause of osteoporosis. Osteoporotic fractures are a major cause of morbidity in older women.
Sample Requirements
Second morning void (spot) urine (1 mL) or a 24h urine collection with no preservative. Specimens containing blood or are extensively haemolysed are not valid.
Storage and Transport
Store at 2-8°C for up to 72 hours, -20°C for longer term storage. Send by overnight first class post.
Turnaround Time
Assay is carried out once every two weeks.
Price
Price available on application - please contact adrian.turner@kch.nhs.uk. Discounts could be available for significant workloads.
Contacts
Ms Tracy Dew Tel: 020 3299 4134. e-mail: tracy.dew@kch.nhs.uk
