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Bone turnover markers (CTX and P1NP): do you have a baseline?
Osteoporosis & Bone Health | Last Active: 3 days ago | Replies (270)Comment receiving replies
NTX can be measured from either serum or urine (usually the second morning void), so that’s likely the one the phlebotomist mentioned.
Of the tests, CTX is the most affected by timing and food. NTX varies a bit less. CTX reaches its lowest point between about 11am to 3pm, so it’s best done first thing in the morning after a fast (and ideally no biotin or collagen for 48 hours beforehand).
Fasting helps, but timing matters more. A 2:30pm draw will probably show a lower CTX, which makes trends harder to interpret. If blood draws are tough, a urine NTX is a good alternative - easier to collect and less time-sensitive. Ive read though, it shows more day-to-day variability and is generally less sensitive than CTX in tracking treatment response. Still, you have to make the best of the situation you’re in, and consistency in how it’s done will still give you useful information over time. It will be helpful to double-check with your ordering physician about timing and sample type to help ensure the most reliable results.
Sorry things haven’t been easy as you’re fighting on two fronts. Wishing you smooth sailing and good results ahead!
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@mayblin Your information is so helpful! I just picked up my original order from the Quest Lab phlebotomist who confirmed that it is the NTX test that Quest will do as a urine test and not as the serum test which my doctor ordered.
So that's something I need to clarify with my doc and point out that most labs do the urine rather than serum, and I think the better results from the urine test must be why. Perhaps her hospital lab only does the serum version...I don't know. Haven't heard back from my doctor about whether she will change her order to urine. so will have to send her a message.
Meanwhile, the clock is ticking with that infusion appointment tomorrow. As much as I'd prefer to have these tests done using my port, it seems relying on the conventional blood draw early in the morning (as I tried to do yesterday) following a fast is what I must try again. Since consistency is also key, I can't rely on the availability of an infusion lab and port going forward.
Will wait a few days (to let my arm heal after uncooperative vein needle sticks) and try another lab and see if better luck there.
Thank you again for such solid information based on lots of research I know. What would we do without the help of people like you. You are truly a major part of our medical teams!