Stegman M R, Recker R R, Davies K M, Ryan R A, Heaney R P
School of Medicine, Creighton University, Omaha, Nebraska 68178.
Osteoporos Int. 1992 Nov;2(6):290-7. doi: 10.1007/BF01623185.
Both retrospectively and prospectively designed studies consistently show low bone mass and/or bone mineral content (BMC) to be risk factor for low-trauma fractures in postmenopausal women. Along with the reports of such studies there has been concern expressed that BMC measurements overlap between fracture groups, i.e., some women with high BMC develop fractures and some women with low BMC do not. In these commonly used epidemiologic study designs, BMC does not discriminate between those who have and have not experienced the untoward event at some level of the exposure factor. The ability to discriminate is more properly determined by the sensitivity and specificity of the measured value. To contrast the concepts of risk and sensitivity, a nested case-control study was conducted within a 24-year cohort study of women at risk for osteoporosis. We found that for each 1.0 decrement of BMC z-scores, the adjusted relative risk for the prospective study design was 1.67, while the odds ratio obtained from the most recent BMC z-score measurements was 1.87. A receiver operating characteristic (ROC) curve, calculated from the nested case-control study data, showed that BMC z-scores, measured after low-trauma fracture, have both low sensitivity and low specificity to detect existing fracture status.
回顾性和前瞻性设计的研究均一致表明，骨量低和/或骨矿物质含量（BMC）是绝经后女性低创伤骨折的危险因素。随着此类研究报告的出现，人们担心骨折组之间的BMC测量值存在重叠，即一些BMC高的女性会发生骨折，而一些BMC低的女性则不会。在这些常用的流行病学研究设计中，BMC在暴露因素的某个水平上无法区分经历过和未经历过不良事件的人群。区分能力更确切地由测量值的敏感性和特异性来确定。为了对比风险和敏感性的概念，在一项针对有骨质疏松风险女性的24年队列研究中进行了一项巢式病例对照研究。我们发现，BMC z评分每降低1.0，前瞻性研究设计的调整后相对风险为1.67，而从最新的BMC z评分测量中获得的优势比为1.87。根据巢式病例对照研究数据计算的受试者工作特征（ROC）曲线显示，低创伤骨折后测量的BMC z评分在检测现有骨折状态方面敏感性和特异性均较低。
