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Background: The Elecsys β-CrossLaps serum assay measures type I collagen degradation fragments (β-CTx) that contain the β-isomerized octapeptide EKAHD-β-GGR. We investigated the analytical performance of the assay and changes in β-CrossLaps in patients with metabolic bone diseases. Methods: The electrochemiluminescent sandwich immunoassay uses two monoclonal antibodies directed against different regions of the linear EKAHD-β-GGR. Results: β-CrossLaps (β-CTx) immunoreactivity was stable in serum and plasma stored at 4 °C for 24 h or at room temperature for 4 h, and it did not decrease appreciably in samples stored at −30 °C for 12 weeks. Nine cycles of repeated freezing-thawing did not affect serum β-CTx. The intra- and interassay imprecision (CVs) for four samples was ≤2.6% (n = 10) and ≤4.1% (n = 10), respectively. The mean day-to-day biological variation (CV) was 20% in 10 postmenopausal women (n = 10 days). Serum β-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 β-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 β-CrossLaps serum assay provides a potentially useful tool for assessing bone resorption state, including its response to estrogen replacement therapy.

Atherosclerosis has two key components, thickening and stiffening of arterial wall. These parameters are quantified ultrasonographically by IMT (intima-media thickness) and PWV (pulse wave velocity). In the present study, we determined the FA IMT (IMT of the bilateral femoral artery) and PWV of femoral-ankle (PWV fa) and brachial-ankle (PWV ba) segments in order to examine whether the degree of atherosclerosis is different between paretic and non-paretic lower limbs in 24 patients with hemiparesis. The values of PWV fa, PWV ba and FA IMT were all significantly greater on the paretic than the non-paretic side. Furthermore, significant decreases in masses of muscle, bone and fat, determined by dual-energy X-ray absorptiometry, were observed in paretic lower limbs compared with the non-paretic side. PWV fa correlated significantly and negatively with muscle mass ( r =-0.488, P =0.0004) and tended to correlate negatively with BMC (bone mineral content; r =-0.264, P =0.069) when statistical analyses were performed with the paretic and non-paretic sides together. Multiple regression analysis elucidated that the muscle mass was associated significantly with PWV fa and PWV ba, independent of age, duration after cerebrovascular accident, gender, bone and fat mass and FA IMT. The muscle mass was still associated with increased PWV fa and PWV ba when multivariate analysis was conducted independently in the paretic and non-paretic sides. In summary, our results indicated that arterial thickening and stiffening were greater on the paretic than the non-paretic side and suggested that a decrease of muscle mass might be associated with increased arterial stiffening in the paretic lower limb.

The newly developed Elecsys Beta-CrossLaps/serum assay measures C-terminal telopeptide of type I collagen and has thus been proposed as a reliable serum marker for bone resorption. We investigated its usefulness for monitoring the therapeutic effect of estrogen replacement therapy on bone turnover and bone mineral density (BMD) in patients with postmenopausal osteoporosis. Serum Beta-CTx decreased by 43.2% +/- 9.2% (mean +/- SD), and 55.1% +/- 7.0% at 3 and 6 months, respectively, after initiation of estrogen replacement therapy (ERT), which was significantly greater than the respective value of urinary excretion of deoxypyridinoline (DPD) (27.8% +/- 4.1%, 34.1% +/- 4.9%, respectively) or pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) assay (14.5% +/- 4.1%, 13.1% +/- 5.0%, respectively). The percent reduction in serum Beta-CTx at 1, 3, and 6 months after initiation of ERT was significantly correlated in a negative manner with the percent increase in spinal BMD at 6 months. Further, ROC analysis to determine the significance of the percent change in bone resorption markers after 3 months of ERT in predicting the gain in spine BMD after 6 months suggested that serum Beta-CTx and urinary DPD might provide a more discriminating indicator than serum ICTP. In conclusion, the findings suggest that the Elecsys Beta-CrossLaps/serum assay provides a sensitive, and thus useful, tool for assessing bone resorption state in Japanese patients.