Interpreting CTX Values

Question

I was on Fosamax for 5 years, but have not taken this drug for almost 5 years.  I need to have some invasive dental work and read about the lab test called the CTX
(C-terminal telopeptide).    

This test is not well known in Sydney, Australia however, where I live.  The results which came back were called ‘Urine Telopeptide (TEL-O).  NTx/Creatinine Ratio: 43 nm/mm Cr (26-124). Does anyone know how to interpret these results? I have read that CTX values above 150 pg/ mL are good, but  I believe these are USA values.  Would you know what the equivalent Australian values would be?

Answer 1

Dear Sydney
Plasma(blood) CTX (collagen telopeptide-X)values above 150 pg/ mL are  considered to be good, but there is controversy regarding it's predictability as a marker for osteocyte activity.  Sorry, I can't help you in the Australian conversion.

Answer 2

Hi there,

It seems as if you are confusing two different sets of tests for bone resorption, i.e. excessive bone loss. There is a CTX test, but there is also something called the N-telopeptide or NTx test. Apparently, based on the results you have provided, your doctor gave you the NTx test, not the CTX test, and that is why the numbers are confusing to. It is not an Australian/US conversion issue, based on the information you have given.

In terms of results for the NTx, in general, a number between 30 to the mid-40’s bone collagen equivalent units/mmol creatinine is considered normal as far as bone turnover is concerned.

As far as the CTX test, it is currently considered to be more accurate than other bone resorption tests. CTX values above 150 pg/mL represent minimal risk, as mentioned by Dr. Grossman.