C-terminal telopeptide
Encyclopedia
In bone physiology
, the C-terminal telopeptide (or more formally, carboxy-terminal collagen crosslinks, and known by the acronym CTX) is a serum
biomarker
used to measure the rate of bone turnover
. It can be useful in assisting clinicians to determine a patient's nonsurgical treatment response as well as evaluate a patient's risk of developing complications during healing following surgical intervention. The test used to detect the CTX marker is called the Serum CrossLaps, and it is more specific to bone resorption than any other test currently available.
use and impaired bone physiology was noted. The strong inhibition of osteoclast
function precipitated by bisphosphonate therapy can lead to inhibition of normal bone turnover, leading to impaired wound healing following trauma (such as dental surgery) or even spontaneous non-healing bone exposure. Because bisphosphonates are preferentially deposited in bone with high turnover rates, it is possible that the levels of bisphosphonate within the jaw bones are selectively elevated.
exist for measuring the metabolic products of bone resorption, the serum CTX marker was chosen because it is both highly correlated to bone turnover rate and already available for detection in a laboratory test carried out by a major lab testing corporation.
The CTX test measures for the presence and concentration of a crosslink peptide
sequence of type I collagen
, found, among other tissues, in bone. This specific peptide sequence relates to bone turnover because it is the portion that is cleaved by osteoclast
s during bone resorption, and its serum levels are therefore proportional to osteoclastic activity at the time the blood sample is drawn. Serum levels in healthy patients not taking bisphosphonates tends to hover above 300 pg/mL.
Patients who are placed on a 6-month drug holiday
exhibit marked improvements in their serum CTX values; in one study, patients showed an improvement of 155.3 pg/mL over 6 months or a rate of 25.9 pg/mL each month.
Initially, urinary CTX levels were sought, but this proved to offer no greater value than urinary NTX values—both tests suffered from large spontaneous fluctuations unrelated to therapy or intervention, and were therefore largely unreliable. In contrast, the monoclonal antibody test for detecting serum CTX levels features minimal spontaneous disruption yet remarkable change to antiresorptive therapy, making the serum CTX assay both highly sensitive and specific
.
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
, the C-terminal telopeptide (or more formally, carboxy-terminal collagen crosslinks, and known by the acronym CTX) is a serum
Blood serum
In blood, the serum is the component that is neither a blood cell nor a clotting factor; it is the blood plasma with the fibrinogens removed...
biomarker
Biomarker (medicine)
In medicine, a biomarker is a term often used to refer to a protein measured in blood whose concentration reflects the severity or presence of some disease state...
used to measure the rate of bone turnover
Bone remodeling
Bone remodeling is a lifelong process where mature bone tissue is removed from the skeleton and new bone tissue is formed...
. It can be useful in assisting clinicians to determine a patient's nonsurgical treatment response as well as evaluate a patient's risk of developing complications during healing following surgical intervention. The test used to detect the CTX marker is called the Serum CrossLaps, and it is more specific to bone resorption than any other test currently available.
Bisphosphonate-associated osteonecrosis of the jaw
In the early 2000s, a link between bisphosphonateBisphosphonate
Bisphosphonates are a class of drugs that prevent the loss of bone mass, used to treat osteoporosis and similar diseases...
use and impaired bone physiology was noted. The strong inhibition of osteoclast
Osteoclast
An osteoclast is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone . This process is known as bone resorption. Osteoclasts were discovered by Kolliker in 1873...
function precipitated by bisphosphonate therapy can lead to inhibition of normal bone turnover, leading to impaired wound healing following trauma (such as dental surgery) or even spontaneous non-healing bone exposure. Because bisphosphonates are preferentially deposited in bone with high turnover rates, it is possible that the levels of bisphosphonate within the jaw bones are selectively elevated.
Risk determination
With the advent of implant dentistry, more dental patients are undergoing therapies in the oral cavity that involve bone healing, such as surgical implant placement and bone grafting procedures. In order to evaluate the risk of osteonecrosis for a patient taking bisphosphonates, use of the CTX biomarker was introduced in 2000 by Rosen.Use of the CTX biomarker
Although a number of surrogate biomarkersSurrogate endpoint
In clinical trials, a surrogate endpoint is a measure of effect of a certain treatment that may correlate with a real clinical endpoint but doesn't necessarily have a guaranteed relationship...
exist for measuring the metabolic products of bone resorption, the serum CTX marker was chosen because it is both highly correlated to bone turnover rate and already available for detection in a laboratory test carried out by a major lab testing corporation.
The CTX test measures for the presence and concentration of a crosslink peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
sequence of type I collagen
Type-I collagen
Type-I collagen is the most abundant collagen of the human body.It is present in scar tissue, the end product when tissue heals by repair.It is found in tendons, the endomysium of myofibrils and the organic part of bone.- See also :* Collagen...
, found, among other tissues, in bone. This specific peptide sequence relates to bone turnover because it is the portion that is cleaved by osteoclast
Osteoclast
An osteoclast is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone . This process is known as bone resorption. Osteoclasts were discovered by Kolliker in 1873...
s during bone resorption, and its serum levels are therefore proportional to osteoclastic activity at the time the blood sample is drawn. Serum levels in healthy patients not taking bisphosphonates tends to hover above 300 pg/mL.
Patients who are placed on a 6-month drug holiday
Drug holiday
A drug holiday is when a patient stops taking a medication for a period of time; anywhere from a few days to many months or even years if they feel it is in their best interests.Planned drug holidays are used in numerous fields of...
exhibit marked improvements in their serum CTX values; in one study, patients showed an improvement of 155.3 pg/mL over 6 months or a rate of 25.9 pg/mL each month.
Initially, urinary CTX levels were sought, but this proved to offer no greater value than urinary NTX values—both tests suffered from large spontaneous fluctuations unrelated to therapy or intervention, and were therefore largely unreliable. In contrast, the monoclonal antibody test for detecting serum CTX levels features minimal spontaneous disruption yet remarkable change to antiresorptive therapy, making the serum CTX assay both highly sensitive and specific
Sensitivity and specificity
Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...
.