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Test Code SNTX N-terminal Telopeptide (NTx), Serum


Specimen Required


Patient Preparation: A morning collection from fasting patients is preferred due to diurnal variation of markers and food effects.

 

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic screw-top aliquot tube

Specimen Volume: 0.5 mL

Collection Instructions: A morning collection from fasting patients is preferred. If not possible, collect the baseline and subsequent specimens under the same circumstances (eg, at same time of day).


Useful For

Monitoring effectiveness of antiresorptive therapy in patients treated for osteoporosis or other metabolic bone disorders

 

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

Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Reporting Name

NTX-Telopeptide, S

Specimen Type

Serum

Specimen Minimum Volume

0.1 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Frozen (preferred) 28 days
  Refrigerated  24 hours

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

Mild OK; Gross reject

Icterus

Mild Ok; Gross reject

Other

Clinical Information

Human bone is continuously remodeled through the process of bone formation and resorption. Measurement of bone turnover markers (BTM) in serum or urine serves as an indicator of bone formation or bone resorption cellular activities. BTM 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. Bone diseases occur when formation and resorption are uncoupled. In these situations, BTM might serve as predictors of therapy response.

 

Telopeptides of type 1 collagen are the most extensively studied and used bone resorption markers. There are 2 forms depending on the cross-link forming site with collagen: the N-terminal telopeptide (NTx) and C-terminal telopeptide (CTX), which are released during collagen degradation.

 

In osteoporosis, a disease characterized by low bone mass and deterioration of bone tissue leading to increase skeletal fragility, measurement of BTM helps to determine treatment efficacy or patient’s compliance with therapy. The advantage of measurement of BTM is that changes in response to therapy are observed within 3 to 6 months after therapy initiation; whereas changes in bone mineral density are not observed until 12 to 24 months posttherapy. Other diseases affecting the bone remodeling process, such as hyperthyroidism, all forms of hyperparathyroidism, most forms of osteomalacia and rickets (even if not associated with hyperparathyroidism), hypercalcemia of malignancy, Paget disease, multiple myeloma, bony metastases, as well as various congenital diseases of bone formation and remodeling, can result in accelerated and unbalanced bone turnover and elevation of BTM.

Reference Values

All units are reported in nmol Bone Collagen Equivalents (BCE)

Adult (≥18 years of age)

 

Males:

5.4-24.2 nmol BCE

 

Females:

Premenopausal: 6.2-19.0 nmol BCE

The target value for postmenopausal adult females undergoing treatment for osteoporosis is the same as the premenopausal reference interval.

Interpretation

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

 

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

 

A common target of antiresorptive therapy in the treatment of postmenopausal osteoporosis is to achieve bone markers concentrations within the premenopausal reference range.

Cautions

Serum N-terminal telopeptide (NTx) should not be used for the screening or diagnosis of osteoporosis. In patients with other clinical conditions known to affect bone resorption (eg; cancer metastases to bone), interpretation of serum NTx for monitoring response to osteoporosis therapy might be unreliable.

 

Do not interchange the Osteomark NTx serum assay values with the Osteomark NTx urine assay values, especially when monitoring therapy.

 

Some patients who have been exposed to animal antigens, either in the environment or as part of treatment or imaging procedures, may have circulating antianimal antibodies present. These antibodies may interfere with the assay reagents to produce unreliable results.

Clinical Reference

1. Lee J, Vasikaran S: Current recommendations for laboratory testing and use of bone turnover markers in management of osteoporosis. Ann Lab Med 2012;32(2):105-112

2. Chopin F, Biver E, Funck-Brentano T, et al: Prognostic interest of bone turnover markers in the management of postmenopausal osteoporosis. Joint Bone Spine 2012;79(1):26-31

3. Hlaing TT, Compston JE: Biochemical markers of bone turnover-uses and limitations. Ann Clin Biochem 2014;51(Pt 2):189-202

Method Description

The Osteomark N-terminal telopeptide (NTx) serum assay is a competitive-inhibition enzyme-linked immunosorbent assay (ELISA/EIA) for quantitative determination of NTx in human serum.

 

NTx epitope is adsorbed onto a 96-well microplate. Diluted samples are added to the microplate wells, followed by a horseradish peroxidase-labeled monoclonal antibody. NTx in the patient sample competes with the NTx epitope in the microplate well for antibody-binding sites. Following a wash step, the amount of labeled antibody bound is measured by colorimetric generation of a peroxide substrate. Absorbance is determined spectrophotometrically and the NTx concentration calculated using a standard calibration curve. Assay values are reported in nanomoles bone collagen equivalents per liter (nM BCE).( Package insert: Osteomark NTx Serum, Alere Scarborough Inc, Scarborough, ME, REV 05/2016)

Day(s) and Time(s) Performed

Tuesday, Thursday; 10 a.m.

Analytic Time

1 day

Specimen Retention Time

14 days

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

82523

LOINC Code Information

Test ID Test Order Name Order LOINC Value
SNTX NTX-Telopeptide, S In Process

 

Result ID Test Result Name Result LOINC Value
65558 NTX-Telopeptide, S In Process