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

在有关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具有快速且相对便宜的优势,而仅需要少量样本量。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定干扰和基质效应的优势,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,六种不同的测定),Delta4-androstenedione (A,四种测定),雌酮 (E(1),一种测定) 和17β-雌二醇 (E(2),五个试验),通过间接试验在20名绝经后妇女的代表性子集中获得测量结果,这些妇女是一项大型前瞻性队列研究的一部分。对于所有测试的直接测定,受试者按相对激素水平排名的批内再现性良好 (类内相关性> 0.89)。在批次之间,就皮尔逊相关性而言,再现性通常也是可接受的 (r > 0.80) 至良好 (r> 0.90)。就类内相关性而言,批次间的可重复性在皮尔逊相关性方面系统地较低,但是,由于测量绝对规模的批次间变化。对于大多数测试的T,A,和E(1) (0.70和0.89之间的皮尔逊相关性),但对于仅针对E(2) 测试的五个试剂盒中的两个试剂盒 (0.86和0.84的相关性) 来说是很高的。在绝对规模上,直接测定的平均测量值通常高于间接测定的平均测量值,并且对于每种激素,根据所使用的试剂盒,其差异很大。总体而言,这项研究的结果表明,通过仔细选择,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,可以在流行病学研究中可靠地估计相对风险。然而,测定绝对规模的标准化仍然存在问题。

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