This kit replaces the NTx-Urine (Osteomark®) N-Terminal Telopeptide of Type I Collagen kit (9006). These two kits are identical in raw materials used, manufacturing process, and QC parameters.

The ZEUS ELISA NTx Urine Test System is an immunoassay that provides a quantitative measurement of the excretion of cross-linked N-telopeptides of type I collagen (NTx) in human urine samples and can be used as an indicator of human bone resorption. Elevated levels of urinary NTx indicate elevated human bone resorption.

Measurement of NTx is intended for the following uses:

  • Predicting skeletal response (bone mineral density) to hormonal antiresorptive therapy in postmenopausal women.
  • Therapeutic monitoring of antiresorptive therapy in postmenopausal women.
  • Therapeutic monitoring of antiresorptive therapy in individuals diagnosed with osteoporosis.
  • Therapeutic monitoring of antiresorptive therapy in individuals diagnosed with Paget’s disease of bone.
  • Therapeutic monitoring of estrogen-suppressing therapies.
  • Identifying the probability for a decrease in bone mineral density after one year in postmenopausal women receiving calcium supplement relative to those treated with hormonal antiresorptive therapy.

This test is for in-vitro diagnostic use only.


Quick Facts

  • Range: 20 – 3000 nM nM BCE
  • Sample Volume: 2 x 25 µl
  • Sample Type: Urine



Bone is a dynamic and evolving tissue. Bone tissue undergoes constant bone turnover which involves the destruction of bone (bone resorption) followed by the construction of new bone (bone formation). In mammals, this continuous remodeling of bone is accomplished through a coupled process of osteoclast mediated bone resorption, followed by osteoblast mediated bone formation. This process is necessary for normal development and maintenance of the skeleton. When balanced, resorption and formation result in healthy bone tissue. If there should be an abnormal imbalance in these two processes, this may result in changes in skeletal mass and shape.

NTx is a collagen degradation product that functions as a marker of bone resorption. Approximately 90% of the organic matrix of bone tissue is type I collagen. NTx is generated from the amino terminus of the type 1 collagen by cleavage of the N-terminal region by cathepsin K during the resorption phase of bone turnover.

Bone turnover markers such as NTx have clinical utility in the comprehensive evaluation of osteoporosis. Elevated concentrations of NTx indicate elevated levels of bone resorption. When interpreted with caution and with a good understanding of its natural variability, measurement of NTx may provide information that supplements osteoporosis management and provide useful clinical information about the conditions that alter bone turnover.


Assay Principle

The ZEUS ELISATM NTx Urine assay is a competitive-inhibition enzyme-linked immunosorbent assay (ELISA) that utilizes microwells as the solid phase onto which NTx has been adsorbed. NTx in the specimen competes with the solid phase NTx for binding sites of a monoclonal antibody labeled with horseradish peroxidase. The amount of antibody bound to the solid phase is therefore inversely proportional to the amount of NTx in the specimen. Quantitation of the NTx concentration in the specimen is determined spectrophotometrically and calculated from a standard calibration curve.


 A 1 Plate Antigen coated 96-microwell plate. 12 x 8-well strips coated with purified human NTx antigen.
B 0.4 mL vial Antibody Conjugate Concentrate. Solution containing purified murine monoclonal antibody directed against NTx conjugated to horse radish peroxidase and Proclin™ 300 (0.1%). Supplied as a 100X concentrated conjugate.
C 30 mL bottle Antibody Conjugate Diluent. Buffered reagent with protein stabilizers, into which Antibody Conjugate Concentrate is diluted. ProClin™ 300 (0.05%) included as a preservative.
D 125 mL bottle 30X Wash Buffer Solution. One bottle containing a 30X ionic detergent solution.
E 0.9 mL bottle Chromogen Reagent. One vial containing a solution of 3,3’,5,5’ – tetramethylbenzidine in dimethyl-sulfoxide. Supplied as a 100x concentrate.
F 30 mL bottle Buffered Substrate. One bottle containing a buffered hydrogen peroxide solution.
G 25 mL bottle Stopping Reagent. One bottle containing a solution of 1N sulfuric acid.
1 0.4 mL vial 1 nM BCE Calibrator Various amounts of purified NTx antigen in a buffered diluent. Contains ProClin™ 300 (0.05%) as a preservative.
2 0.4 mL vial 30 nM BCE Calibrator
3 0.4 mL vial 100 nM BCE Calibrator
4 0.4 mL vial 300 nM BCE Calibrator
5 0.4 mL vial 1000 nM BCE Calibrator
6 0.4 mL vial 3000 nM BCE Calibrator
I 0.4 mL vial Level I Urine Control Human urine with known NTx concentration. ProClin™ 300 (0.10%) included as a preservative.
II 0.4 mL vial Level II Urine Control
Plate Sealers 1 pad

Measurement range:

20 to 3000 nM Bone Collagen Equivalents (BCE).


Expected Values:

Category n= Average NTx

(nM BCE)

Min NTx

(nM BCE)

Max NTx

(nM BCE)

Median NTx

(nM BCE)

Males, < 25 YOA 25 1821 33 3150 1740
Males, 26-50 YOA 25 743 128 1862 704
Males, > 50 YOA 25 780 79 2602 744
Females, 18-35 YOA 25 723 64 2685 525
Females, > 50 YOA 50 601 49 1852 481


Limitations of the procedure:

While the ZEUS NTx Urine assay is used as an indicator of bone resorption, the use of this test has not been established to predict development of osteoporosis or future fracture risk. Use of this test has not been established in primary hyperparathyroidism or hyperthyroidism. When using the ZEUS NTx Urine assay to monitor therapy, results may be confounded in patients afflicted with clinical conditions known to affect bone resorption, e.g., metastases to bone. While a ZEUS NTx Urine assay value provides a measure of the level of bone resorption, a single ZEUS NTx Urine assay value cannot provide the rate of bone resorption as reported results do not contain a measure of time. The ZEUS NTx Urine assay results should be interpreted in conjunction with clinical findings and other diagnostic results.