Cole L A, Kardana A
Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, CT 06510.
Clin Chem. 1992 Feb;38(2):263-70.
Discordance has been reported in human chorionic gonadotropin (hCG) concentrations measured by different immunoassay kits. We examined the results for 40 serum samples assayed with 10 different hCG immunoassay kits. Results varied considerably. Individual sample results varied by as much as 58-fold. Average results for different kits varied by as much as 1.4-fold for pregnancy (20 samples) and 2.2-fold for trophoblast disease (20 samples) serum. We investigated the causes of this discordance. hCG or hCG beta are general names for mixtures of hCG, hCG alpha, or hCG beta immunoreactive molecules in serum. These mixtures include regular hCG, nicked hCG (missing peptide linkages at beta 44-45 or beta 47-48), carbohydrate variants of hCG, hCG missing the beta-subunit C-terminal segment, free beta-subunit, beta-core fragment, and free alpha-subunit. We prepared standards for each of these major variants and measured their reactivities in the 10 hCG immunoassay kits. Free beta-subunit reactivity varied from nonrecognition (anti-beta:anti-alpha type kits; Hybritech Tandem-R and others) to overrecognition (one kit had five-fold greater affinity for free beta than for hCG). Kits with antibodies to beta-subunit C-terminal segment (Organon NML and others) failed to recognize hCG missing this segment, a component of serum hCG in trophoblast disease. Kits with anti-hCG antibodies (Serono MAIA-clone and others) had minimal recognition of nicked hCG (12%), a component of all serum hCG samples, and consistently gave the lowest values with all serum samples. We conclude that differences in recognition of nicked hCG, free beta, and these other hCG variants cause discordance in hCG immunoassay results.
不同免疫分析试剂盒检测人绒毛膜促性腺激素（hCG）浓度时曾有不一致的报道。我们检测了用10种不同hCG免疫分析试剂盒检测的40份血清样本的结果。结果差异很大。单个样本结果的差异高达58倍。不同试剂盒对妊娠（20份样本）血清的平均结果差异高达1.4倍，对滋养层疾病（20份样本）血清的差异高达2.2倍。我们研究了这种不一致的原因。hCG或hCGβ是血清中hCG、hCGα或hCGβ免疫反应性分子混合物的通用名称。这些混合物包括正常hCG、缺口hCG（β44 - 45或β47 - 48处肽键缺失）、hCG的碳水化合物变体、缺失β亚基C末端片段的hCG、游离β亚基、β核心片段和游离α亚基。我们为每种主要变体制备了标准品，并在10种hCG免疫分析试剂盒中测量了它们的反应性。游离β亚基的反应性差异很大，从无法识别（抗β:抗α型试剂盒；Hybritech Tandem - R等）到过度识别（一种试剂盒对游离β的亲和力比对hCG高五倍）。含有β亚基C末端片段抗体的试剂盒（Organon NML等）无法识别缺失该片段的hCG，而这是滋养层疾病血清hCG的一个组成部分。含有抗hCG抗体的试剂盒（Serono MAIA - clone等）对缺口hCG的识别能力极低（12%），缺口hCG是所有血清hCG样本的一个组成部分，并且对所有血清样本的检测结果始终最低。我们得出结论，对缺口hCG、游离β以及其他hCG变体识别的差异导致了hCG免疫分析结果的不一致。
