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EPIC CODE: LAB5258 N-terminal Telopeptide, Serum

Additional Codes

Sunquest: SNTXM
Mayo:        SNTX

Specimen Required

Patient Preparation: Fasting is preferred due to diurnal variation of markers and food effects.

Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. 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).

2. Centrifuge and aliquot serum into a plastic vial.

Secondary ID


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


This test is not useful for screening or diagnosing osteoporosis.


Measurement of serum N-terminal telopeptide is helpful for monitoring effectiveness of antiresorptive therapies in patients treated for osteoporosis or other metabolic bone disorders.

Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Reporting Name

NTX-Telopeptide, S

Specimen Type


Specimen Minimum Volume

0.1 mL

Specimen Stability Information

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

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

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, N-terminal telopeptide and C-terminal telopeptide, 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)



5.4-24.2 nmol BCE



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.


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


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


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.


In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies [HAMA] or heterophile antibodies), which may cause interference in some immunoassays. Caution should be used in interpretation of results, and the laboratory should be alerted if the result does not correlate with the clinical presentation.

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 Mar;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 Jan;79(1):26-31

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

Method Description

The Osteomark N-terminal telopeptide (NTx) serum assay is a competitive-inhibition enzyme-linked immunosorbent assay 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/L).(Package insert: Osteomark NTx Serum. Alere Scarborough, Inc; REV 05/2016)

Day(s) Performed

Monday, Thursday

Report Available

2 to 5 days

Specimen Retention Time

3 months

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US 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


LOINC Code Information

Test ID Test Order Name Order LOINC Value
SNTX NTX-Telopeptide, S 21215-9


Result ID Test Result Name Result LOINC Value
65558 NTX-Telopeptide, S 21215-9

NY State Approved