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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
Convinced my endocrinologist to order bone marker turnover tests as a baseline before my Reclast infusion which has been recommended by my breast cancer oncologist.
Today I went to Quest Labs with her order for these tests:
N-telopeptide Cross-Linked Serum (NTx)
C-telopeptide beta cross linked serum (CTx)
Procollagen type I Intact N-Terminal Propertied (P1NP)
Parathyroid Hormone Intact Without Calcium.
The Quest phlebotomist said she could not do a blood test on one of these tests, but it could be done with a urine test. She tried to contact my ordering physician to clarify blood or urine, but was unable to because it was too early. Decided to proceed with the 3 tests she could run. That's when problem #2 occurred. She could not successfully stick me despite 2 attempts (arm and hand). I can be a tough stick which is why I have a port for my chemotherapy. Unfortunately, Quest and most outpatient labs do not use ports.
I had fasted for 12 hours but drank 32 ounces of water between 6-7 am. My Quest appointment was at 7:30 am. Usually the hydration helps and the Quest phlebotomists have been successful on first sticks in the past. Unfortunately, the mastectomy/node biopsy means I should only use my left side. Today, alas, was not a successful blood draw.
Since there was confusion about one of the tests (urine or serum) and difficulty in sticking me, the phlebotomist and I agreed I should cancel that appointment, she would try to get more information from my doc, and then try again. Quest could do a urine test but not that specified serum test.
After that long-winded setup here's my actual question. I just found out my cancer infusion lab will accept this order for the bone markers even though the doctor is not on their staff. That will make it so much easier for me for the blood tests. If one of these tests must be a urine test, rather than a blood test, I'll get that elsewhere.
But my infusion appointment is at 2:30 pm. I cannot change this appointment as it's tied to seeing my oncologist immediately afterwards. From what I've read here these tests should be done after fasting but also ideally first thing in the morning. How unreliable would these tests be if done at 2:30 pm? I could probably hold out for an 8 hour fast. Or should I just hope for the best and go back and try again with conventional blood draws and needle sticks?
I guess yet another example of accepting things you can't control.
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@prarysky
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!