Premium
Biological Variability of Serum and Urinary N‐Telopeptides of Type I Collagen in Postmenopausal Women
Author(s) -
Eastell R.,
Mallinak N.,
Weiss S.,
Ettinger M.,
Pettinger M.,
Cain D.,
Flessland K.,
Chesnut C.
Publication year - 2000
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.2000.15.3.594
Subject(s) - medicine , urine , morning , urinary system , bone resorption , type i collagen , bone remodeling , postmenopausal women , urology , endocrinology
Measurement of N‐telopeptides of type I bone collagen (NTX) provides a specific indicator of the current level of bone resorption. The biological intrasubject variability of NTX in urine and serum was studied in 277 postmenopausal women, mean age, 63.6 years ± 10.2 (±SD) years. Second‐morning void urine and serum specimens were collected at baseline and for two consecutive days to determine short‐term variability (%CV). Long‐term variability was determined by comparing NTX results at baseline and two consecutive months. Subjects were instructed to maintain current diet, lifestyle, and medications during the study. The median short‐term %CV was 13.1% for urine NTX. This compared with 6.3% for serum NTX. Calculation of long‐term %CV showed similar trends, with the %CV for NTX measured in serum (7.5%) lower than when measured in urine (15.6%). Using the least significant change (LSC) calculation, our data show that to be 90% confident that a decrease in NTX after initiation of antiresorptive therapy in an individual patient is not caused by variability alone, a 31% decrease in urine NTX and a 14% decrease in serum NTX is required. As reported changes in NTX caused by antiresorptive therapy are greater than these calculations; our results support the use of either specimen to measure NTX to monitor the effect of therapy.