Serum/Plasma Concentration of Carboxyterminal Peptide of Type I Collagen (CTX-I)

What This Test Measures

CTX-I (C-terminal telopeptide of type I collagen) is a marker released when collagen, a key protein in bone, is broken down. It reflects the rate of bone resorption (bone breakdown) and is often used alongside other tests to evaluate conditions affecting bone health, such as osteoporosis or metabolic bone diseases.

Why It Might Be Ordered

Your healthcare provider may order this test if you have symptoms or risk factors for bone-related conditions, such as low bone density, fractures, or certain cancers that affect bone metabolism. It can also help monitor treatment progress for conditions like Paget’s disease or hyperparathyroidism.

Common Uses and Conditions

CTX-I is commonly used to diagnose or monitor osteoporosis, Paget’s disease, and other bone disorders. It may also be checked in patients with kidney disease, since kidney function can affect how well CTX-I is cleared from the body.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is then separated into serum (the liquid part) or plasma (similar but contains clotting factors). This test does not require fasting, but follow your provider’s instructions for any special preparation.