Update Type: Test Code Change
Test Updated: 12/07/2022
Test Overview
Test Methodology


Test Usage

This test is used for monitoring effectiveness of antiresorptive therapy in patients treated for osteoporosis or other metabolic bone disorders or as an adjunct in the diagnosis of medical conditions associated with increased bone turnover.

Reference Range *

All units are reported in nmol Bone Collagen Equivalents (BCE). Adult Male: 5.4-24.2 nmol BCE; Adult Female, Premenopausal: 6.2-19.0 nmol BCE.

Test Limitations

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.

Test Details
Days Set Up
Tuesday, Thursday
Analytic Time

2 - 6 days

Soft Order Code
MiChart Code
NTx Serum (Sendout)
  • N-Telopeptides, Serum
  • Pyrrolinks-D, Serum
  • Crosslinked N-telopeptide of Type 1 Collagen, Serum
  • Type I Collagen (NTX), Serum
  • Collagen Crosslinks, Serum
  • FNTX
  • N-Telopeptide, Cross-Linked, Serum
Reference Laboratory
Special Testing
Specimen Requirements
Collection Instructions

Collect specimen in a red top or SST tube from a fasting patient (preferred). Centrifuge, aliquot serum into a plastic vial and freeze.

This test 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.
Fasting Specimen
A morning collection from fasting patients is preferred. If not possible, collect the baseline and subsequent specimens under the same circumstances (e.g., at same time of day).
Normal Volume
0.5 mL serum
Minimum Volume
0.1 mL serum
Additional Information

Test sent to Mayo Medical Laboratories.

CPT Code
Fee Code
NY State Approved