Clinical evaluation of the Elecsys beta-CrossLaps serum assay, a new assay for degradation products of type I collagen C-tlopeptides.
BACKGROUND
The Elecsys beta-CrossLaps serum assay measures type I collagen degradation fragments (beta-CTx) that contain the beta-isomerized octapeptide EKAHD-beta-GGR. We investigated the analytical performance of the assay and changes in beta-CrossLaps in patients with metabolic bone diseases.


METHODS
The electrochemiluminescent sandwich immunoassay uses two monoclonal antibodies directed against different regions of the linear EKAHD-beta-GGR.


RESULTS
beta-CrossLaps (beta-CTx) immunoreactivity was stable in serum and plasma stored at 4 degrees C for 24 h or at room temperature for 4 h, and it did not decrease appreciably in samples stored at -30 degrees C for 12 weeks. Nine cycles of repeated freezing-thawing did not affect serum beta-CTx. The intra- and interassay imprecision (CVs) for four samples was < or = 2.6% (n = 10) and < or = 4.1% (n = 10), respectively. The mean day-to-day biological variation (CV) was 20% in 10 postmenopausal women (n = 10 days). Serum beta-CTx and osteocalcin were correlated in patients with hyperparathyroidism (r = 0.796; P <0.0001; n = 28), chronic renal failure on hemodialysis (r = 0.784; P = 0.0003; n = 16), hypoparathyroidism (r = 0.950; P = 0.0001; n = 11), and pseudohypoparathyroidism (r = 0.987; P = 0.130; n = 4). Serum beta-CTx decreased by 47.4% +/- 8.8% (mean +/- SD) and 60.7% +/- 6.5% at 3 and 6 months, respectively, after initiation of estrogen replacement therapy in 34 women. These decreases were greater than the decreases in urinary excretion of deoxypyridinoline (31.8% +/- 3.9% and 38.1% +/- 4.4%, respectively) or pyridinoline cross-linked C-terminal telopeptide of type I collagen (15.9% +/- 3.9% and 16.9% +/- 4.6%, respectively).


CONCLUSIONS
The Elecsys beta-CrossLaps serum assay provides a potentially useful tool for assessing bone resorption state, including its response to estrogen replacement therapy.
Okabe
R
R
Department of Metabolism, Endocrinology and Molecular Medicine, Osaka City University Graduate School of Medicine, Osaka 545-8585, Japan.
Nakatsuka
K
K
Inaba
M
M
Miki
T
T
Naka
H
H
Masaki
H
H
Moriguchi
A
A
Nishizawa
Y
Y
D015415:Biomarkers / Q000097:blood; D001851:Bone Diseases, Metabolic / Q000097:blood*; D003094:Collagen / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D024042:Collagen Type I; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood; D007011:Hypoparathyroidism / Q000097:blood; D007118:Immunoassay / Q000379:methods; D007676:Kidney Failure, Chronic / Q000097:blood / Q000628:therapy; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000097:blood / Q000188:drug therapy; D010446:Peptide Fragments / Q000276:immunology; D010455:Peptides / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D011547:Pseudohypoparathyroidism / Q000097:blood; D011933:Reagent Kits, Diagnostic; D006435:Renal Dialysis; D012680:Sensitivity and Specificity
D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011933:Reagent Kits, Diagnostic; C052929:collagen type I trimeric cross-linked peptide; D003094:Collagen