NTX-Telopeptide, Urine (NTXPR)

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Test Code: NTXSO

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

Collagen Crosslinks

Crosslinked N-telopeptide of Type I Collagen (NTX), Urine

N-Telopeptide, Urine

NTX Creatinine

Osteomark

Osteoporosis

Useful For

1. An adjunct in the diagnosis of medical conditions associated with increased bone turnover

2. The differential diagnosis of osteomalacia versus osteoporosis

3. Identifying individuals with osteoporosis with elevated bone turnover and consequent increased risk for rapid disease progression

4. Prediction of bone densitometry response to antiresorptive therapy of osteoporosis

5. Monitoring and assessing effectiveness of therapy in patients treated for osteopenia, osteoporosis, Paget disease, or other disorders treated with antiresorptive therapy

6. An adjunct in monitoring response to other therapeutic intervention in diseases with increased bone turnover (eg, rickets, osteomalacia, hyperthyroidism)

Indications 3 through 5 have been endorsed by the Negotiated Rulemaking Committee of HCFA and are therefore federally reimbursed.

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
Urine	Clean, plastic urine collection container		4 mL	0.5 mL

Collection Processing Instructions

1. Collect second morning void.
2. No preservative.

(24 hour volume is no longer required)

Specimen Stability Information

Specimen Type	Temperature	Time
Urine	Frozen (preferred)	30 days
	Refrigerated	14 days
	Ambient	72 hours

Rejection Criteria

Grossly Hemolyzed

Specimen with pH <5

Specimen containing preservatives

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Analytical Time	Methodology/Instrumentation
Mayo Medical Laboratories	Monday through Friday	1-2 days	NTXCT: VITROS Competitive Chemiluminescence Immunoassay NTXCT: Enzymatic Colorimetric Assay

Reference Lab

Mayo Clinic Laboratories

Test Information

Test assesses bone resorption and is useful in assessing response to therapy (hormone replacement therapy, allendronate, or calcitonin). Results are reported as a ratio to urine creatinine in molar units. Serial values are required for assessing significant change. Generally a decrease of 30% or more from baseline (pre-intervention) level indicates efficacious therapy and will correlate with bone mineral density measurements. Collect baseline and post-therapy specimens at the same time of day and under similar conditions. A post-therapy specimen at 2-6 months following treatment is generally recommended. Biochemical bone markers are generally not useful for the diagnosis of osteoporosis. Test is FDA-approved.

Reference Range Information

All units are reported in nmol Bone Collagen Equivalents/mmol creatinine.
Adult (> or =18 years of age)
Males:
21-83 nmol BCE/mmol creatinine
Females:
Premenopausal: 17-94 nmol BCE/mmol creatinine
Postmenopausal: 26-124 nmol BCE/mmol creatinine
Pediatric
Males:
Tanner Stage I: 55-508 nmol BCE/mmol creatinine
Tanner Stage II: 21-423 nmol BCE/mmol creatinine
Tanner Stage III: 27-462 nmol BCE/mmol creatinine
Tanner Stage IV: <609 nmol BCE/mmol creatinine
Tanner Stage V: <240 nmol BCE/mmol creatinine
Females:
Tanner Stage I: 6-662 nmol BCE/mmol creatinine
Tanner Stage II: 193-514 nmol BCE/mmol creatinine
Tanner Stage III: 13-632 nmol BCE/mmol creatinine
Tanner Stage IV: <389 nmol BCE/mmol creatinine
Tanner Stage V: <132 nmol BCE/mmol creatinine

Interpretation

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

Most patients with osteopenia or osteoporosis have low, but unbalanced, bone turnover, with bone resorption dominating over bone formation. While this may result in mild elevations in bone turnover markers in these patients, finding significantly elevated urine NTx levels is atypical. Therefore, if levels are substantially elevated above the young adult reference range (>1.5- to 2-fold), the likelihood of coexisting osteomalacia, or of an alternative diagnosis as described in the Clinical Information section, should be considered.

When alternative causes for elevated NTx have been excluded in an osteopenia/osteoporosis patient, the patient must be considered at increased risk for accelerated progression of osteopenia/osteoporosis.

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

The Negotiated Rulemaking Committee of HCFA also recommends:

"Because of significant specimen to specimen collagen crosslink physiologic variability (15%-20%), current recommendations for appropriate utilization include: 1 or 2 baseline assays from specified urine collections on separate days; followed by a repeat assay about 3 months after starting antiresorptive therapy; followed by a repeat assay in 12 months; thereafter not more than annually, if medically necessary."

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
82523		1	Collagen cross links, any method
82570		1	Creatinine, other source