Comparison of the analytical and clinical performance characteristics of an N-MID versus an intact osteocalcin immunoradiometric assay
Comparison of the analytical and clinical performance characteristics of an N-MID versus an intact osteocalcin immunoradiometric assay
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DOI：
10.1016/s0009-8981(99)00251-x
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发表时间：
2000-04-01
影响因子：
5
通讯作者：
Inoue, T
中科院分区：
文献类型：
--
作者：
Takahashi, M;Kushida, K;Inoue, T
骨钙素是骨中含量最丰富的非胶原蛋白，反映其形成过程。据报道，完整的骨钙素的不稳定性是由于骨钙素的C端序列裂解产生一个大的N端骨钙素片段所致。建立了一种检测骨钙素N端片段和完整骨钙素的两点免疫分析方法，这两种方法都不依赖于不稳定的C端序列。本研究的目的是研究N-MID骨钙素免疫放射测定法的性能，并与完整的骨钙素测定法进行比较。10份血清样本反复冷冻，解冻7次。N-MID骨钙素的变异性小于完整骨钙素。4℃保存7天后血清骨钙素的稳定性，N-MID的平均值为初始值的94.3%，完好值为73.4%。2、5、7d后，原始值的下降幅度明显大于N-MID。在零下30摄氏度，N-MID的值在长达10周的时间内没有变化。用N-MID骨钙素和完整骨钙素测定了27例绝经前、27例绝经后和68例骨质疏松患者(23例椎体骨折，35例髋部骨折)的骨钙素浓度。绝经后受试者骨钙素较绝经前受试者平均增加的百分比在N-MID中为98%，而在完整测定中为42%。N-MID和INTERNAL的Z分数在所有组中显示相似的结果。N-MID骨钙素水平与完整骨钙素呈显著正相关(r=0.755)，与其他骨形成生化标志物如骨特异性碱性磷酸酶(r=0.606)和I型前胶原C末端前肽(r=0.568)呈显著正相关。N-MID IRMA在储存过程中的稳定性好于完整的IRMA，并具有与完整的绝经后和骨质疏松的鉴别能力相似的能力。因此，N-MID骨钙素IRMA可以提高骨钙素的临床应用和评价。(C)2000 Elsevier Science B.V.保留所有权利。
Osteocalcin is the most abundant non-collagenous protein in bone, reflecting its formation. It was reported that the instability of intact osteocalcin results from the cleavage of the C-terminal sequence of osteocalcin to produce a large N-terminal osteocalcin fragment. A two-site immunoassay for detecting both the N-terminal osteocalcin fragment and the intact osteocalcin was developed that were both independent of an unstable C-terminal sequence. The aim of this study is to investigate the performance of an N-MID osteocalcin immunoradiometric assay and to compare it with an intact osteocalcin assay. Ten serum samples were repeatedly frozen and thawed up to seven times. The variability of the values of N-MID osteocalcin was less than that of the intact osteocalcin. For stability of osteocalcin in serum after storage, the mean value of N-MID was 94.3% of the initial value after 7 days at 4 degrees C, whereas the intact was 73.4%. The reduction of intact values were significantly larger than that of N-MID after 2, 5 and 7 days. At - 30 degrees C, the values of N-MID did not change for up to 10 weeks. The concentrations of osteocalcin measured by an N-MID osteocalcin and an intact osteocalcin were investigated in 27 premenopausal subjects, 27 postmenopausal subjects, and 68 osteoporotic patients (23 with vertebral fractures and 35 with hip fractures). The percent mean increase of osteocalcin in postmenopausal subjects over premenopausal subjects was 98% in N-MID versus 42% in the intact assay. The z-scores of N-MID and intact showed similar results in all groups. N-MID osteocalcin si,significantly correlated with intact osteocalcin (r = 0.755), and other biochemical markers for bone formation, such as bone specific alkaline phosphatase (r = 0.606) and C-terminal propeptide of type I procollagen (PICP) (r = 0.568). An N-MID IRMA had better stability during storage than intact and had the discriminative ability which is similar to the intact assay in postmenopause and osteoporosis. Therefore, an N-MID osteocalcin IRMA could improve the clinical utility and evaluation of osteocalcin. (C) 2000 Elsevier Science B.V. All rights reserved.