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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).

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

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
Serum Frozen (preferred) 28 days
  Refrigerated  24 hours

Reject Due To


Mild OK; Gross reject


Mild OK; Gross reject


Mild Ok; Gross 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: 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)



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 (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.

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

Day(s) and Time(s) Performed

Tuesday, Thursday; 10 a.m.

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


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