N-Telopeptide Cross-links (NTx), Urine

Create a Free Account to View Prices

Turnaround Time: 2 - 4 days
CPT Code:

82570, 82523

Test Type: 20 mL Urine
Stability Time:



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Reference Range:


• Pediatric: see table.1

• Adults:

− Male: 0−62 nM BCE/mmol creatinine

− Female: 20 to 49 years 0−64 nM BCE/mmol creatinine; >49 years 0−89 nM BCE/mmol creatinine

Tanner Stage


(nM BCE/mmol creatinine)


(nM BCE/mmol creatinine)

















Evaluation of osteoporosis and assessment of antiresorptive therapy.

Approximately 90% of the organic matrix of mammalian bone consists of type I collagen that is cross-linked at the N-terminal and C-terminal ends.1 This highly cross-linked structure provides for the basic fabric and tensile strength of bone tissue. The collagen infrastructure of bone undergoes a continuous process of remodeling that involves osteoclast-mediated bone resorption and osteoblast-mediated bone formation. Osteoporosis occurs when there is an imbalance between bone formation and bone resorption leading to net bone loss.2-5 Certain aspects of this bone composition and structure that contribute to increased bone fragility may not be captured by bone mineral density measurements.5

Bone resorption by osteoclasts results in the production of cross-linked N-telopeptides of type I collagen (NTx).1 NTx is specific to bone and is found in urine as a stable end product of bone degradation. Levels of NTx correlate with the rate of bone resorption. Bone resorption rates exceeding bone formation results in a net loss of bone and ultimately osteopenia or osteoporosis.2-8 Osteoporotic fractures are a major source of morbidity and mortality in older women.2 The NTx test is intended for use in predicting skeletal response to hormonal antiresorptive therapy in postmenopausal women. The NTx test can also be used to monitor the efficacy of antiresorptive therapy7 in postmenopausal women, women with osteoporosis, and individuals with Paget disease. The NTx test can also be used in monitoring the effect of estrogen-suppressing therapies on the rate of bone resorption. A recent study8 supported the use of NTx to identify the probability of a decrease in bone mineral density after one year in postmenopausal women receiving a calcium supplement relative to those treated with hormonal antiresorptive therapy.

Several studies have shown that certain biochemical markers of bone turnover, measured in serum or urine, can be used as independent predictors of fractures, especially spine and hip.2,6 Bone mineral density (BMD) is often used to monitor the efficacy of osteoporosis treatment and to follow patient compliance. Unfortunately, changes in BMD in response to treatment are slow, and it takes at least one year of treatment before a significant change in BMD can be observed in many cases.2,7 As a result, the absence of BMD increase does not necessarily indicate a lack of therapeutic response.2,7 The use NTx can be helpful for assessing early changes in BMD (baseline vs post-treatment) revealing a biological effect of the medication and proving patient compliance and persistence.2,7

1. Endres DB, Rude RK. Mineral and bone metabolism. In Burtis CA, Ashwood ER, eds. Tietz Textbook of Clinical Chemistry. 3rd ed. Philadelphia, Pa: WB Saunders Co; 1999:1349-1457. PubMed 9799819

2. Sweet MG, Sweet JM, Jeremiah MP, Galazka SS. Diagnosis and treatment of osteoporosis. Am Fam Physician. 2009 Feb 1; 79(3):193-200. PubMed 19202966

3. Bergmann P, Body JJ, Boonen S, et al. Evidence-based guidelines for the use of biochemical markers of bone turnover in the selection and monitoring of bisphosphonate treatment in osteroporosis: A consensus document of the Belgian Bone Club. Int J Clin Pract. 2009 Jan; 63(1):19-26. PubMed 19125989

4. Lewiecki EM. Managing osteoporosis: Challenges and strategies. Cleve Clin J Med. 2009 Aug; 76(8):457-466. PubMed 19652039

5. Poole KE, Compston JE. Osteoporosis and its management. BMJ. 2006 Dec 16; 333(7581):1251-1256. PubMed 17170416

6. Singer FR, Eyre DR. Using biochemical markers of bone turnover in clinical practice. Cleve Clin J Med. 2008 Oct; 75(10):739-750. PubMed 18939390

7. Garnero P, Shih WJ, Gineyts E, Karpf DB, Delmas PD. Comparison of new biochemical markers of bone turnover in late postmenopausal osteoporotic women in response to alendronate treatment. J Clin Endocrinol Metab. 1994; 79(6):1693-1700. PubMed 7989477

8. Garnero P, Sornay-Rendu E, Chapuy MC, Delmas PD. Increased bone turnover in late postmenopausal women is a major determinant of osteoporosis. J Bone Miner Res. 1996 Mar; 11(3):337-349. PubMed 8852944

Collection Details:

Collection Instructions:

Values obtained with different assay methods should not be used interchangeably in serial testing. It is recommended that only one assay method be used consistently to monitor each patient's course of therapy. This procedure does not provide serial monitoring; it is intended for one-time use only. If serial monitoring is required, please order test 511097.

Plastic urine container without preservative.

Collect a second void of the morning or an aliquot of a 24-hour urine (no preservative). When monitoring therapy, baseline samples should be collected prior to initiation of therapy. Subsequent specimens should be collected at the same time of day as baseline specimens.