Novel Algorithm for Free Testosterone Determination

描述(由申请人提供)：睾酮水平的测量是诊断男性和女性雄激素紊乱的核心。循环中的睾丸素主要与性激素结合球蛋白(SHBG)和白蛋白结合；只有未结合或游离的部分才具有生物活性。因此，在影响SHBG浓度的情况下，如衰老、肥胖和糖尿病，游离睾酮的测定对于准确评估雄激素状态是必要的。目前测定游离睾酮的方法--平衡透析法、超滤法、示踪剂模拟法和基于质量作用定律的算法--都存在不精密度或不精确度的问题。平衡透析法被广泛认为是参考法，它劳动强度大、操作繁琐，而且容易受到示踪剂杂质的影响而产生误差，这导致内分泌学会的专家小组得出结论：“……计算游离睾酮是对血浆中游离睾酮的最有用的估计……”因此，根据总睾酮、SHBG和白蛋白浓度计算游离睾酮浓度的算法得到了广泛的应用。我们的初步数据表明，目前SHBG上均一的睾酮结合部位的模型是错误的，现有的质量定律作用方程的概念基础是错误的，从现有的质量定律作用方程得出的游离睾酮浓度与平衡透析测得的浓度有很大不同。由于现有方法的这些局限性，需要一种准确的方法来测定游离睾酮浓度，以便在临床实践中方便地应用，这是一个巨大的未得到满足的需求。新的证据表明，睾酮与SHBG的结合符合集合变构模型(EAM)。基于这个新的睾酮与SHBG结合的EAM模型，我们构建了一个计算游离睾酮水平的新算法，该算法与平衡透析测定的值具有很好的一致性。第一阶段SBIR应用旨在通过确定新算法的精密度、准确度、功能灵敏度、试验内和试验间变异以及特异性、稳定性和基质效应来表征新算法的技术性能(目标1)。AIM 2将在算法中加入SHB基因，并将其应用于具有不同SHBG基因的男性。目标3将描述该分析在年轻和老年男性和女性以及SHBG浓度变化的肥胖男性中的表现。第一阶段研究的产品将是一个受版权保护的经过验证的算法，可以作为一个独立的应用程序提供，医生可以在他们的个人电脑或手持设备上下载，以便在他们的办公室甚至床边使用。一个跨学科的研究团队，强大的初步数据，以及符合FDA指导的验证计划将确保成功开发出一种有相当大的未满足需求的产品，这将促进我们对睾酮与SHBG结合的理解。

DESCRIPTION (provided by applicant): The measurement of testosterone levels is central to the diagnosis of androgen disorders in men and women. Circulating testosterone is bound largely to sex hormone binding globulin (SHBG) and albumin; only the unbound or free fraction is biologically active. Therefore, in conditions that affect SHBG concentrations, such as aging, obesity, and diabetes, the determination of free testosterone is necessary to obtain an accurate assessment of androgen status. The current methods for the determination of free testosterone - equilibrium dialysis, ultrafiltration, tracer analog methods, and the use of algorithms based on the law-of-mass-action - suffer from problems of imprecision or inaccuracy. Equilibrium dialysis method, widely considered the reference method, is labor-intensive and cumbersome, and susceptible to errors due to tracer impurities, leading the Endocrine Society's Expert Panel to conclude that "...the calculation of free testosterone is the most useful estimate of free testosterone in plasma..." Therefore, algorithms for calculating free testosterone concentrations from total testosterone, SHBG and albumin concentrations using the law-of-mass-action equations have been used widely. Our preliminary data show that the current model of homogeneous testosterone binding sites on SHBG - the conceptual basis of the extant law-of-mass action equations - is erroneous, and that the free testosterone concentrations derived from the available law-of-mass action equations differ substantially from those measured by equilibrium dialysis.. Because of these limitations of the available methods, there is an enormous unmet need for an accurate method to determine free testosterone concentrations that can be applied conveniently in clinical practice. New evidence shows that testosterone's binding to SHBG conforms to an Ensemble Allostery Model (EAM). Based on this new EAM model of testosterone binding to SHBG, we have constructed a novel algorithm for calculating free testosterone levels that provides excellent conformity with values determined by equilibrium dialysis. This phase I SBIR application aims to characterize the technical performance of the novel algorithm by determining its precision, accuracy, functional sensitivity, intra- and inter-assay variation, and specificity, stability, and matrix effects (Aim 1). Aim 2 will incorporate SHB genotype in the algorithm and apply it to men with different SHBG genotypes. Aim 3 will characterize the performance of the assay in young and older men and women, and in obese men with alterations in SHBG concentrations. The product of the phase I studies will be a copyright-protected validated algorithm available as a stand-alone application that physicians can download on their personal computers or hand-held devices for use in their office or even on the bedside. An interdisciplinary team of investigators, strong preliminary data, and a validation plan that conforms to FDA guidance will assure the successful generation of a product for which there is considerable unmet need and which will advance our understanding of testosterone's binding to SHBG.