Critical differences in the serial measurement of three biochemical markers of bone turnover in the sera of pre- and postmenopausal women.
OBJECTIVE
The purpose of this investigation was to quantify the biologic, day-to-day variability and critical differences in serum levels of crosslinked collagen N-telopeptides (NTx), procollagen aminoterminal extension propeptides (PINP) and bone specific alkaline phosphatase (bAP) in healthy women.


METHODS
Seven blood samples were collected from 12 pre- and 15 postmenopausal women over 4 to 6 months. NTx, PINP and bAP levels were determined utilizing enzyme- and radioimmunoassay techniques.


RESULTS
The within-subject coefficient of variation (C.V.) in serum bAP, NTx and PINP levels was 7.1, 10.6 and 12.4% respectively. These variances did not differ significantly among premenopausal women when compared with postmenopausal subjects. Combining terms for analytical and biologic variability revealed that a critical difference between 2 successive serial measurements is 24% for bAP, 34% for NTx and 38% for PINP.


CONCLUSIONS
Circulating levels of NTx, PINP and bAP are stable over time periods of several months, allowing for the determination of significant changes in skeletal metabolism of women.
Scariano
J K
JK
Medical Laboratory Sciences, Department of Pathology, HSSB Room 220, University of New Mexico School of Medicine, Albuquerque, New Mexico 87131-5651, USA. Jscariano@salud.unm.edu
Garry
P J
PJ
Montoya
G D
GD
Wilson
J M
JM
Baumgartner
R N
RN
D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000469:Alkaline Phosphatase / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D001862:Bone Resorption / Q000097:blood* / Q000000981:diagnostic imaging; D003094:Collagen / Q000097:blood*; D024042:Collagen Type I; D005260:Female; D006801:Humans; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood*; D010455:Peptides / Q000097:blood*; D017698:Postmenopause / Q000502:physiology*; D017697:Premenopause / Q000502:physiology*; D011347:Procollagen / Q000097:blood*; D013997:Time Factors; D014463:Ultrasonography
D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C047202:procollagen Type I N-terminal peptide; D003094:Collagen; D000469:Alkaline Phosphatase