In large-scale epidemiological studies on endogenous sex steroids and cancer risk, direct immunoassays of circulating hormone levels have the advantage of being fast and comparatively inexpensive while requiring only small sample volumes. On the other hand, indirect assays after organic extraction and chromatographic prepurification have the advantage of reducing specific interferences and matrix effects and hence are thought to have better validity. We compared direct assays of testosterone (T, six different assays), Delta4-androstenedione (A, four assays), estrone (E(1), one assay), and 17beta-estradiol (E(2), five assays) with measurements obtained by an indirect assay in a representative subset of 20 postmenopausal women who were part of a large prospective cohort study. Within-batch reproducibilities of the subject rankings by relative hormone levels were good (intraclass correlations >0.89) for all direct assays tested. Between batches, reproducibilities generally were also acceptable (r > 0.80) to good (r > 0.90) in terms of Pearson's correlations. The between-batch reproducibility in terms of intraclass correlations was systematically lower in terms of Pearson's correlations, however, because of between-batch variations in the absolute scale of measurements. The relative validity of direct versus indirect assays in terms of the subjects' ranking by relative hormone levels was also high for most of the kits tested for T, A, and E(1) (Pearson's correlations between 0.70 and 0.89) but was high for only two kits of five tested for E(2) (correlations of 0.86 and 0.84). On an absolute scale, mean measurement values were generally higher for direct assays than for the indirect assay and, for each hormone, varied substantially, depending on the kit used. Overall, the results of this study show that, with careful selection, commercial kits for direct radioimmunoassays of steroid hormones in postmenopausal serum can be found that may allow a reliable estimation of relative risks in epidemiological studies. However, standardization of the absolute scale of assays remains problematic.

译文

:在关于内源性类固醇和癌症风险的大规模流行病学研究中,循环激素水平的直接免疫测定法具有快速且相对便宜的优点,而只需要少量样品。另一方面,有机萃取和色谱预纯化后的间接测定具有减少特异性干扰和基质效应的优点,因此被认为具有更好的有效性。我们比较了睾丸激素的直接测定(T,六个不同的测定),Delta4-雄烯二酮(A,四个测定),雌酮(E(1),一个测定)和17β-雌二醇(E(2),五个测定)的测量结果。通过间接测定从20名绝经后妇女的代表性子集中获得,这些妇女是大型前瞻性队列研究的一部分。对于所测试的所有直接测定,按相对激素水平进行的受试者等级的批内重现性均良好(类内相关性> 0.89)。在批次之间,就皮尔逊相关性而言,重现性通常也可接受(r> 0.80)至良好(r> 0.90)。就类内相关性而言,批间的可重复性就皮尔逊相关性而言是系统地较低的,但是,由于批处理之间的变化在绝对测量范围内。对于大多数针对T,A和E(1)进行测试的试剂盒,按照受试者相对激素水平对受试者的直接或间接测定的相对有效性也很高(Pearson相关系数在0.70和0.89之间),而对于只有两个试剂盒(五个试剂盒)进行了E(2)测试(相关系数为0.86和0.84)。在绝对尺度上,直接测定的平均测量值通常比间接测定的高,并且对于每种激素,根据所使用的试剂盒,其平均测量值会有很大差异。总的来说,这项研究的结果表明,经过精心选择,可以发现用于绝经后血清中类固醇激素直接放射免疫测定的商业试剂盒,可以对流行病学研究的相对风险做出可靠的估计。然而,测定的绝对规模的标准化仍然存在问题。

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