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Serum C-telopeptide (CTX) is commonly used for diagnosing and monitoring patients with osteoporosis. This test measures the amount of bone turnover products circulating in the bloodstream by detecting the C-terminal telopeptide of type I collagen - a protein component of bone.

Test at a glance

Clinical Utility
​Used to diagnose patients with osteoporosis and to monitor their treatment by detecting clinically relevant change in bone breakdown.

Ordering
​Healthcare provider needs to indicate ‘CTX’ in the ‘Other Tests’ section of the requisition form.

Patient instructions

​Patient needs to bring the completed requisition form to a Patient Service Centre. 

Turnaround Time
​Test results will be available within 2 weeks.

Cost

​This test is not currently covered by provincial health plans, but may be covered by the patient’s private insurance.

Healthcare Professional Information

​What is Being Tested?


Serum CTX can detect clinically-relevant change in bone resorption that occurred over as little as a few months, unlike bone mineral density (BMD) radiologic tests which require several years of bone loss to generate a measurable output.1 Consequently CTX is able to provide better guidance for treatment plans. Serum CTX is the most established test of bone breakdown used in clinical trials of osteoporosis drugs. In combination with BMD test, serum CTX test may be used to enhance the estimation of the future risk of bone fractures. 2

Patient Frequently Asked Questions(FAQs)

​How is it used?

CTX is commonly used for diagnosing and monitoring patients with osteoporosis.

When is it ordered?

CTX is used in men and women who are at high risk for fractures – for instance those whose clinical history, bone mineral density (BMD), thyroid hormones, calcium and vitamin D tests suggest they may be at risk of osteoporosis.1 It is also used for people who are about to start taking medications for osteoporosis, who can use this test to help monitor the success of their therapy. 2

Because of the high inter-individual variability of bone turnover markers, the optimal strategy is to determine a baseline CTX value for the patient and then repeat testing in several months to observe the change in the patients bone-turnover status.

What does the test result mean?

Elevated levels of CTX indicate increased bone resorption. Increased levels are associated with osteoporosis, osteopenia, Paget disease, hyperthyroidism, and hyperparathyroidism.

In patients taking antiresorptive agents (bisphosphonates or hormone replacement therapy), a decrease of less or equal to 25% from baseline CTx levels (ie, prior to the start of therapy) 3 to 6 months after initiation of therapy indicates an adequate therapeutic response.

Is there a charge for the test?

This test is not covered by the provincial health insurance plans*, but it may be covered by extended health insurance plans. Contact LifeLabs to find out about the current fee for the test.

References

  1. Current Recommendations for Laboratory Testing and Use of Bone Turnover Markers in Management of Osteoporosis. Lee J et al, Ann Lab Med, 2012; 32(2): 105–112.
  2. Bone Turnover Markers In The Management Of Postmenopausal Osteoporosis. Brown JP et al, Clinical Biochemistry, 2009; 42:929-942.

Additional Resources

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