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Longitudinal evaluation of a bone resorption marker in elderly subjects
A M Bollen1, H A Kiyak, D R Eyre
1Department of Orthodontics, University of Washington, Seattle 98195, USA.
Summary
Bone resorption marker collagen type I N-telopeptide crosslink (NTx) shows consistent excretion over time in elderly individuals. This finding supports using NTx levels to identify those at higher risk for osteoporotic fractures.
Area of Science:
- Gerontology
- Biochemistry
- Orthopedics
Background:
- Bone resorption is a key factor in osteoporosis.
- Collagen type I N-telopeptide crosslink (NTx) is a validated marker for bone resorption.
- Understanding the long-term variability of NTx is crucial for clinical application in elderly populations.
Purpose of the Study:
- To evaluate the within-subject variability of NTx excretion over a 2-year period in community-dwelling elderly individuals.
- To compare NTx excretion between men and women.
- To assess the reproducibility of NTx measurements for identifying high bone turnover.
Main Methods:
- Collected three annual 24-hour urine samples from 93 elderly participants (mean age 73).
- Measured NTx concentration using ELISA.
- Analyzed total NTx excretion and NTx/creatinine ratio, employing Kendall's rank correlation for consistency.
Main Results:
- Men exhibited significantly lower NTx/creatinine excretion than women not on hormone replacement therapy.
- The within-subject long-term coefficient of variability for NTx/creatinine was 26%.
- Kendall's coefficient of concordance for NTx excretion over three years was 0.78, indicating significant reproducibility.
Conclusions:
- NTx excretion demonstrates acceptable long-term reproducibility in elderly individuals, comparable to daily variations.
- The consistency of NTx measurements supports its use in stratifying subjects by bone resorption levels.
- Identifying individuals with high bone turnover using NTx can aid in predicting osteoporotic fracture risk.