Analysis of hCG: Clinical Applications and Assay Requirements

Sturgeon, Catharine M.; McAllister, E Jean

doi:10.1177/000456329803500402

Cited by 41 publications

(28 citation statements)

References 77 publications

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“…To this end the IFCC Working Group for human chorionic gonadotropin (hCG) 8 established an unambiguous and user-friendly nomenclature that describes hCG and its 6 most important isoforms, and subsequently prepared the 1st WHO International Reference Reagents (IRRs) for these 6 isoforms (1,3 ). The 6 isoforms were prepared by use of previously developed purification methods, which included hydrophobic interaction chromatography and reversed-phase HPLC (3 ).…”

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confidence: 99%

“…The nonbioactive ␣ and ␤ subunits were assigned units based on mass, with 1 g of each corresponding to 1 IU of the relevant IRP. Thus units for hCG and its subunits are not directly related, so it is difficult to compare results for the various forms of hCG to assess the extent to which they are recognized in different immunoassay systems (7,8 ). The presence of impurities and nicked forms of hCG in the 3rd and 4th IS was an additional reason to prepare new standards (1 ).…”

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Differences in Recognition of the 1st WHO International Reference Reagents for hCG-Related Isoforms by Diagnostic Immunoassays for Human Chorionic Gonadotropin

et al. 2009

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Background: The 1st WHO International Reference Reagents (IRRs) for 6 human chorionic gonadotropin (hCG)-related molecular variants, highly purified and calibrated in substance concentrations by the IFCC Working Group for hCG, permit experimental elucidation of what commercially available hCG methods measure in molar terms and enable assessment of their fitness for clinical purposes. Methods: Pools containing known amounts of the IRRs spiked into normal human serum were issued to participants through the UK National External Quality Assessment Service for hCG for a period of 7 years. Among 16 assays used, 4 recognized only hCG, whereas 6 recognized hCG and its free β-subunit (hCGβ), and 6 recognized hCG, hCGβ, and the beta core fragment. Results: Differences in calibration of current hCG assays are moderate. Mean recovery of the current International Standard (IS), hCG IS 75/589, was 107% (range 93% to 126%), whereas that of the IRR 99/688 for hCG was 139% (range 109%–164%). Between-method variation for the latter (CV 12.3%) was also greater than for IS 75/589 (CV 8.8%). Recognition of hCGβ varied markedly (CV 37%). Most assays overestimated it, but 2 RIAs produced results that were slight underestimations. Recognition of the beta core fragment was even more variable (CV 57%) and was closest to equimolarity for the RIAs. Conclusions: Assays for hCG show considerable variation in their recognition of various forms of hCG, and this variablility is the most important cause of method-related differences in hCG results in serum and an even more important cause of method-related differences in urine measurements. Equimolar recognition of the major hCG isoforms is essential if between-method comparability for hCG is to be improved.

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Differences in Recognition of the 1st WHO International Reference Reagents for hCG-Related Isoforms by Diagnostic Immunoassays for Human Chorionic Gonadotropin

et al. 2009

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“…The subunits, which have no bioactivity, were assigned arbitrary units based on mass (1 g corresponds to 1 IU). This means that comparing concentrations of the three molecules is difficult, requiring several assumptions and relatively complex calculations to obtain the values in substance concentrations (9 ). Additionally, assessment of cross-reactivity data is hampered by contamination of hCG IS 75/537 with nicked hCG (hCGn), a partially degraded form of hCG that is recognized to different degrees by different immunoassays (1,6 ).…”

Section: Nomenclature For Hcg-related Moleculesmentioning

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Establishment, Value Assignment, and Characterization of New WHO Reference Reagents for Six Molecular Forms of Human Chorionic Gonadotropin

et al. 2004

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“…The role of hCG as a tumor marker in a variety of cancers is of great clinical significance (3,4), and quantitative, specific hCG tests are important in the diagnosis and management of hCGsecreting cancers (5). However, the design criteria of hCG cancer assays differ from those required for pregnancy tests.…”

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Antibody Recognition of a Human Chorionic Gonadotropin Epitope (hCGβ66–80) Depends on Local Structure Retained in the Free Peptide

Gregor

Cerasoli

Schouten

et al. 2011

Journal of Biological Chemistry

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Human chorionic gonadotropin (hCG) is an important biomarker in pregnancy and oncology, where it is routinely detected and quantified by specific immunoassays. Intelligent epitope selection is essential to achieving the required assay performance. We present binding affinity measurements demonstrating that a typical ␤3-loop-specific monoclonal antibody (8G5) is highly selective in competitive immunoassays and distinguishes between hCG␤ 66 -80 and the closely related luteinizing hormone (LH) fragment LH␤ 86 -100 , which differ only by a single amino acid residue. A combination of optical spectroscopic measurements and atomistic computer simulations on these free peptides reveals differences in turn type stabilized by specific hydrogen bonding motifs. We propose that these structural differences are the basis for the observed selectivity in the full protein.The glycoprotein human chorionic gonadotropin (hCG), 2 is a heterodimer consisting of an ␣-and ␤-chain (Fig. 1a) in noncovalent association. Essential in pregnancy and detectable within a few days of fertilization, it has become one of the most frequently assayed hormones, and simple, one-step, antibodybased measurements of hCG are now standard in pregnancy testing. At this early stage of pregnancy, the trophoblast cells of the preimplantation embryo produce a hyperglycosylated form of the hormone, which drives embryonic implantation in the uterine wall (2). Subsequently, hCG regulation by syncytiotrophoblast cells of the placenta promotes and maintains progesterone secretion from the corpus luteum. In other applications, therapeutically injected hCG is the key to in vitro fertilization, where it is used to trigger ovulation and, in males, used to promote testosterone production.The role of hCG as a tumor marker in a variety of cancers is of great clinical significance (3, 4), and quantitative, specific hCG tests are important in the diagnosis and management of hCGsecreting cancers (5). However, the design criteria of hCG cancer assays differ from those required for pregnancy tests. Specifically, different sensitivity ranges are involved, and, for oncology applications, the antibodies used must be able to detect various modified forms of hCG with equal affinity (6). The role of hCG assays in the diagnosis and management of malignant trophoblastic disease (choriocarcinoma) is one of the great success stories of oncology (7,8); it is the ideal tumor marker, always present when choriocarcinoma cells exist, and in quantities directly related to the number of those cells. The correct use of hCG assays in combination with appropriate therapy has led to a survival rate approaching 100% in this otherwise aggressive cancer.All hCG diagnostic tests are carried out as immunoassays, based on specific antibodies that are able to distinguish hCG from three other, closely related, members of the glycoprotein hormone family (luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH)) (9). The ␣-chains of these four hormones are identica...

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Analysis of hCG: Clinical Applications and Assay Requirements

Cited by 41 publications

References 77 publications

Differences in Recognition of the 1st WHO International Reference Reagents for hCG-Related Isoforms by Diagnostic Immunoassays for Human Chorionic Gonadotropin

Differences in Recognition of the 1st WHO International Reference Reagents for hCG-Related Isoforms by Diagnostic Immunoassays for Human Chorionic Gonadotropin

Establishment, Value Assignment, and Characterization of New WHO Reference Reagents for Six Molecular Forms of Human Chorionic Gonadotropin

Antibody Recognition of a Human Chorionic Gonadotropin Epitope (hCGβ66–80) Depends on Local Structure Retained in the Free Peptide

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