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crosslinked N-telopeptide in urine; urine pyridinolone & deoxypyridinolone (OsteoMark)
Urinary marker of bone resorption.
Reference interval:
1) male: 23-110 NTx*
2) female: 13-96 NTx
* NTx = umol bone collagen equivalents (BCE)/mol of creatinine
Clinical significance:
- cross-linked N-telopeptides are formed by collagenase digestion of bone-mineral matrix
- cross-linked N-telopeptides are excreted in the urine & appear to be specific markers of bone resorption
- the assay is especially useful for management of bone loss in osteoporosis*
* Probability of a decrease in bone mineral density with NTx
NTx Probability of decrease
18-38 1.4 p=0.28
38-51 2.4 p=0.03
51-67 3.8 p=0.0006
67-188 17.3 p=0.0001
Increases:
-> clinical disorders
a) Paget's disease
b) hyperparathyroidism
c) osteoporosis
Method:
1) ELISA
2) assays measure N-telopeptide fragments of collagen (non-helical amino-terminal fragments)
3) these fragments contain both pyridinolone & deoxypyridinolone
4) assays are calibrated using a standard of bacterial collagenase-digested human bone collagen
5) results are expressed as equivalent moles of bone collagen type 1 normalized to creatinine
Specimen:
1) urine (2 hour)
2) collect after 8 hour fast
3) store frozen
General
collagen crosslinks
urine chemistry test
References
- Medical Knowledge Self Assessment Program (MKSAP) 11, American
College of Physicians, Philadelphia 1998
- Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed.,
W.B. Saunders, 1995
- Teitz Textbook of Clinical Chemistry and Molecular Diagnostics,
4th edition, Burtis CA, Ashwood ER, Burns DE (eds), Elsevier,
St Louis, 2006, pg 1939
- Panel of 4 tests
Laboratory Test Directory ARUP: 70062
- N-Telopeptide, Cross-Linked, Serum
Laboratory Test Directory ARUP: 70500
Component-of
crosslinked N-telopeptide/creatinine in urine