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Test Code NTXPR NTX-Telopeptide, Urine

Secondary ID

61656

Useful For

As an adjunct in the diagnosis of medical conditions associated with increased bone turnover

 

Monitoring effectiveness of antiresorptive therapy in patients treated for osteopenia, osteoporosis, Paget disease, or other metabolic bone disorders

Profile Information

Test ID Reporting Name Available Separately Always Performed
NTXCT Creatinine, U No Yes
NTXUR NTX-Telopeptide, U No Yes

Method Name

NTXUR: VITROS Competitive Chemiluminescence Immunoassay

NTXCT: Enzymatic Colorimetric Assay

Reporting Name

NTX-Telopeptide, U

Specimen Type

Urine


Specimen Required


Patient Preparation: For 24 hours before this urine collection, do not take multivitamins or dietary supplements containing biotin or vitamin B7 that are commonly found in hair, skin, and nail supplements and multivitamins.

Container/Tube: Plastic, 13-mL urine tube

Specimen Volume: 4 mL

Collection Instructions:

1. Collect second morning void.

2. No preservative.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Frozen (preferred) 30 days
  Refrigerated  14 days
  Ambient  72 hours

Reject Due To

Hemolysis

Mild reject; Gross reject

Lipemia

NA

Icterus

NA

Other

Specimen with pH <5; specimen containing preservatives

Clinical Information

Human bone is continuously remodeled through a process of osteoclast-mediated bone formation and resorption. This process can be monitored by measuring serum and urine markers of bone formation and resorption. Approximately 90% of the organic matrix of bone is type I collagen, a helical protein that is cross-linked at the N- and C-terminal ends of the molecule. The amino acid sequences and orientation of the cross-linked alpha 2 N-telopeptide of type 1 collagen make it a specific marker of human bone resorption. N-terminal telopeptide (NTx) molecules are mobilized from bone by osteoclasts and subsequently excreted in the urine. Elevated levels of NTx indicate increased bone resorption.

 

Bone turnover markers are physiologically elevated during childhood, growth, and during fracture healing. The elevations in bone resorption markers and bone formation markers are typically balanced in these circumstances and of no diagnostic value. By contrast, abnormalities in the process of bone remodeling can result in changes in skeletal mass and shape. Many diseases, in particular hyperthyroidism, all forms of hyperparathyroidism, most forms of osteomalacia and rickets (even if not associated with hyperparathyroidism), hypercalcemia of malignancy, Paget disease, multiple myeloma, and bony metastases, as well as various congenital diseases of bone formation and remodeling can result in accelerated and unbalanced bone turnover. Unbalanced bone turnover, usually without increase in bone turnover, is also found in age-related and postmenopausal osteopenia and osteoporosis.

 

Disease-associated bone turnover abnormalities should normalize in response to effective therapeutic interventions, which can be monitored by measurement of serum and urine bone resorption and formation markers.

Reference Values

All units are reported in nmol Bone Collagen Equivalents/mmol creatinine.

Adult (≥18 years of age)

Males:

21-83 nmol BCE/mmol creatinine

 

Females:

Premenopausal: 17-94 nmol BCE/mmol creatinine

Postmenopausal: 26-124 nmol BCE/mmol creatinine

 

Pediatric

Males:

Tanner Stage I: 55-508 nmol BCE/mmol creatinine

Tanner Stage II: 21-423 nmol BCE/mmol creatinine

Tanner Stage III: 27-462 nmol BCE/mmol creatinine

Tanner Stage IV: <609 nmol BCE/mmol creatinine

Tanner Stage V: <240 nmol BCE/mmol creatinine

 

Females:

Tanner Stage I: 6-662 nmol BCE/mmol creatinine

Tanner Stage II: 193-514 nmol BCE/mmol creatinine

Tanner Stage III: 13-632 nmol BCE/mmol creatinine

Tanner Stage IV: <389 nmol BCE/mmol creatinine

Tanner Stage V: <132 nmol BCE/mmol creatinine

Interpretation

Elevated levels of N-terminal telopeptide (NTx) indicate increased bone resorption.

 

Most patients with osteopenia or osteoporosis have low, but unbalanced, bone turnover, with bone resorption dominating over bone formation. While this may result in mild elevations in bone turnover markers in these patients, finding significantly elevated urine NTx levels is atypical. Therefore, if levels are substantially elevated above the young adult reference range (>1.5- to 2-fold), the likelihood of coexisting osteomalacia, or of an alternative diagnosis as described in the Clinical Information section, should be considered.

 

When alternative causes for elevated NTx have been excluded in an osteopenia/osteoporosis patient, the patient must be considered at increased risk for accelerated progression of osteopenia/osteoporosis.

 

A 30% or greater reduction in this resorption marker 3 to 6 months after initiation of therapy indicates a probably adequate therapeutic response.

 

The Negotiated Rulemaking Committee of HCFA also recommends:

"Because of significant specimen to specimen collagen crosslink physiologic variability (15%-20%), current recommendations for appropriate utilization include: 1 or 2 baseline assays from specified urine collections on separate days; followed by a repeat assay about 3 months after starting antiresorptive therapy; followed by a repeat assay in 12 months; thereafter not more than annually, if medically necessary."

Clinical Reference

1. Miller PD, Baran DT, Bilezikian JP, et al: Practical clinical application of biochemical markers of bone turnover: Consensus of an expert panel. J Clin Densitom 1999;2(3):323-342

2. Delmas PD, Eastell R, Garnero P, et al: The use of biochemical markers of bone turnover in osteoporosis. Committee of Scientific Advisors of the International Osteoporosis Foundation. Osteoporos Int 2000;11(6):S2-S17

3. Mora S, Prinster C, Proverbio MC, et al: Urinary markers of bone turnover in healthy children and adolescents: age-related changes and effect of puberty. Calcif Tissue Int 1998;63:369-374

Day(s) and Time(s) Performed

Monday, Wednesday, Friday; Varies

Analytic Time

1 day

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

82570

82523

LOINC Code Information

Test ID Test Order Name Order LOINC Value
NTXPR NTX-Telopeptide, U In Process

 

Result ID Test Result Name Result LOINC Value
NTXCT Creatinine, U 2161-8
NTX NTX 35334-2
NTXCR NTX-Telopeptide, U 21216-7

Forms

If not ordering electronically, complete, print, and send a General Request Form (T239) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/general-request-form.pdf).