Radioimmunoassay of the serum free beta-subunit of human chorionic gonadotropin in trophoblastic disease

Predictive values of different forms of human chorionic gonadotropin in postmolar gestational trophoblastic neoplasia

OBJECTIVE

The aim of this study was to reach a publicly applicable marker, using the increasing or decreasing trend of different forms of β-human chorionic gonadotropin (β-hCG) during the first 28 days after molar pregnancy evacuation.

METHODS

The present retrospective cohort study investigated all of the documents of patients with hydatidiform mole according to their pathological results during their admission and follow-up in the past 10 years (2003-2013). The type of the relationship was determined using locally weighted scatterplot smoothing (Lowess Smoother) and fractional polynomial regression (Fracpoly), and then a model tailored to data processing was used for drawing the receiver operating characteristic curve. During the investigation of gestational trophoblastic neoplasia (GTN) risk factors, the multiple logistic regression method was used to control the confounding variables.

RESULTS

Among individuals with high-risk molar pregnancy, 11 (18%) had GTN, and the prevalence of GTN in individuals with low-risk molar pregnancy was 13.4%. The slope of the β-hCG line slightly decreases with a rate of change close to zero in individuals with GTN, but the decrease is not statistically significant (P > 0.05). The receiver operating characteristics curve for serum β-hCG measurement after 21 days of molar pregnancy evacuation showed 83% sensitivity at 89% specificity (area under the curve, 0.9), which indicates that this variable has an optimal performance for discrimination between the GTN cases and patients who had spontaneous disease remission. The mean times of reaching the first negative titer in those without neoplasia and reaching a definitive GTN diagnosis were 8.1 (SD, 2) and 6.2 (SD, 1.5), respectively. The most effective remaining variable in the logistic model was uterine size larger than gestational age (95% confidence interval, 0.99-1.31; odds ratio, 1.14) with a slight increase in the risk and borderline significance (P = 0.07).

CONCLUSIONS

The serum β-hCG measurement after 21 days of molar pregnancy evacuation and slope of the linear regression line of β-hCG showed to be a good test to discriminate between patients who will get spontaneous disease remission and patients developing GTN.

Linear regression of postevacuation serum human chorionic gonadotropin concentrations predicts postmolar gestational trophoblastic neoplasia

OBJECTIVE

Currently, human chorionic gonadotropin (hCG) follow-up after evacuation of hydatidiform moles is essential to identify patients requiring chemotherapeutic treatment for gestational trophoblastic neoplasia (GTN). We propose a model based on linear regression of postevacuation serum hCG concentrations for the prediction of GTN.

METHODS

One hundred thirteen patients with at least 3 serum samples from days 7 to 28 after evacuation were selected from the Dutch Central Registry for Hydatidiform Moles (1994-2009). The slopes of the linear regression lines of the first 3 log-transformed serum hCG and free β-hCG values were calculated. Receiver operating characteristic curves were constructed to calculate areas under curve (AUCs).

RESULTS

The slope of the hCG regression line showed an AUC of 0.906 (95% confidence interval, 0.845-0.967). Gestational trophoblastic neoplasia could be predicted in 52% of patients with GTN at 97.5% specificity (cutoff, -0.020). Twenty-one percent of patients with GTN could be predicted before diagnosis according to the International Federation of Gynecology and Obstetrics 2000 criteria. The slope of free β-hCG showed an AUC of 0.844 (95% confidence interval, 0.752-0.935), 69% sensitivity at 97.5% specificity, and 38% of patients with GTN could be predicted before diagnosis according to the International Federation of Gynecology and Obstetrics criteria.

CONCLUSIONS

The slope of the linear regression line of hCG proved to be a good test to discriminate between patients who will achieve spontaneous disease remission and patients developing GTN. The slope of free β-hCG seems to be a better predictor for GTN than the slope of hCG. Although this model needs further validation for different assays, it seems a promising way to predict the more aggressive cases of GTN.

Management of nonpregnant women with elevated human chorionic gonadotropin

Human chorionic gonadotropin (hCG) is useful in evaluating and monitoring early pregnancy as well as trophoblastic disease. Here we describe the management of women with elevated serum human chorionic gonadotropin in a case of a 51-year-old female who was unsuccessfully treated for ectopic pregnancy. She was subsequently diagnosed with pituitary hCG production, which should be considered as differential diagnosis before treatment is initiated.

The diagnostic value of beta-human chorionic gonadotropin, progesterone, CA125 in the prediction of abortions

This study was conducted to investigate the effectiveness of serum levels of free beta-hCG, progesterone, CA125 and their combined use in the prediction of first trimester abortions. A total of 140 singleton pregnant women between 5 and 13 weeks' gestational age were included as Group I (n = 21) who resulted in abortion including missed abortion, incomplete abortion, complete abortion and inevitable abortion; Group II (n = 129) included normal pregnancies. When using the free beta-hCG level of <20 ng/ml as a cut off point, the sensitivity, specificity, PPV and NPV were 91%, 82%, 46% and 98%, when using a progesterone of <15 ng/ml as a cut off point, they were 91%, 89%, 59%, 98%. The single measurement of free beta-hCG or progesterone levels can be useful in the prediction of first trimester spontaneous abortions, but using progesterone may be recommended since it has high availability and low cost.

Biochemical screening for Down’s syndrome in the first trimester of pregnancy

Down’s syndrome (DS) is the commonest single cause of severe mental retardation and accounts for just under a third of all cases. Until the late 1980’s population screening was based on offering amniocentensis to older women. This made little impact on the prevalence of DS because the majority (approximately 70%) of babies with DS are born to women under the age of 35 (Figure 1).

Are Laboratories Reporting Serum Quantitative hCG Results Correctly?

Background: Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein hormone that exists in multiple forms. Immunoassays commonly used in clinical laboratories measure intact hCG, total β hCG (intact hCG + hCG free β-subunit), and/or hCG free β-subunit. Measurement of serum concentrations of hCG is useful for confirmation and monitoring of pregnancy, diagnosis of trophoblastic diseases and monitoring of the efficacy of treatment, and prenatal screening. Correctly reporting results for the various forms of hCG is clinically important.

Method: We prepared samples by addition of intact hCG and hCG free β-subunit to an essentially hCG-free human serum matrix. The samples were analyzed by participant laboratories using various immunoassay methods.

Results: We identified errors in participant reporting of intact hCG results as total β hCG (9.3%; 22 of 235 laboratories) and total β hCG as intact hCG (13.1%; 8 of 61 laboratories).

Conclusions: Many factors contribute to the erroneous reporting of hCG results, including (a) the complexity of hCG molecule and confusion of nomenclature on the various forms of hCG; (b) laboratory personnel’s lack of awareness of the distinctions of the forms of hCG and failure to recognize the specificity of assays for their measurement; (c) lack of clarity and uniformity in manufacturers’ reagent labeling; and (d) most product inserts’ lack of information on the specificity of each method to the various forms of hCG.

Elevated hCG Outside of Pregnancy—Diagnostic Considerations and Laboratory Evaluation

Human chorionic gonadotropin (hCG) is a glycoprotein hormone produced by trophoblastic tissues, and its identification is frequently relied upon to establish the diagnosis of pregnancy. Entities other than pregnancy, such as false-positive hCG results, pituitary hCG, exogenous hCG, and both trophoblastic and nontrophoblastic neoplasias, can also cause laboratory assays for hCG to show positive results. Because of their rarity, these conditions are not commonly recognized, and the steps to differentiate between them are not widely known. Discriminating between the causes of elevated hCG in nonpregnant patients can be confusing. An understanding of the differential diagnosis and awareness of available diagnostic modalities are essential for accurate diagnosis and avoidance of potentially harmful treatments.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to state the importance of types of human chorionic gonadotropin (hCG), recall their presence in both trophoblastic and nontrophoblastic neoplasias, and explain how important it is to distinguish between the various causes of an elevated serum hCG to avoid harmful treatments.

Advances in the clinical laboratory detection of gestational trophoblastic disease

BACKGROUND

Gestational trophoblastic disease (GTD) consists of a spectrum of disorders that are characterized by an abnormal proliferation of trophoblastic tissue. Gestational trophoblastic neoplasia (GTN) refers to a subset of GTD with a persistently elevated serum hCG in the absence of a normal pregnancy and with a history of normal or abnormal pregnancy. Although previously a lethal disease, GTN is considered today the most curable gynecologic cancer. However, a delay in the diagnosis may increase the patient's risk of developing malignant GTN, and therefore the prompt identification of GTN is important.

SERUM MARKERS

hCG test is essential for detection of GTN. It has emerged that there are problems with hCG tests. In addition to regular hCG, at least five major variants of hCG are present in serum samples. False-positive hCG (phantom hCG) can occur in the absence of GTN. Low-level real hCG may occasionally persist in the absence of clinical evidence of pregnancy or GTD. Alternatively, low-level real hCG may be due to pituitary hCG. Other placental hormones, human placental lactogen (hPL), inhibin and activin, and progesterone have also been evaluated as tumor markers for GTD.

CONCLUSION

hCG has high diagnostic sensitivity, approaching 100% sensitivity, for managing the treatment of GTN and for detecting recurrences of disease. It is recommended to use hCG test that recognizes all forms of the hCG molecule. In cases where low-level hCG persists, it must be differentiated whether it is real or false. Real-hCG may be due to quiescent gestational trophoblastic disease or pituitary hCG. It has not yet been established whether measurement of markers other than hCG (hPL, inhibin, activin, and progesterone) is useful in the detection and follow-up of GTD.

Human chorionic gonadotropin in cancer

Human chorionic gonadotropin (hCG) is mainly used for detection and monitoring of pregnancy and pregnancy-related disorders but it is also an extremely sensitive and specific marker for trophoblastic tumors of placental and germ cell origin. Thus treatment of relapsing choriocarcinomas and testicular germ cell tumors is often initiated on the basis of rising hCG levels even in the absence of clinical or histological evidence of a relapse. While these tumors mostly produce the intact heterodimeric hormone consisting of an alpha (hCGalpha), and a beta subunit (hCGbeta), many nontrophoblastic tumors produce only hCGbeta This is usually a sign of aggressive disease and elevated serum levels of hCGbeta are strongly associated with poor prognosis. Elevated serum levels are observed in 45-60% of patients with biliary and pancreatic cancer and in 10-30% of most other cancers. Methods that detect hCG and hCGbeta together are mainly used for measurement of hCG-like immunoreactivity in serum. However, the reference range for hCG is 5-8 fold higher than that for hCGbeta and thus moderately elevated levels can be identified only with a specific and sensitive hCGbeta assay.

Are serum inhibin concentrations new markers of placental tumours in the course of chemotherapy?

BACKGROUND

The study was conducted to evaluate whether the detection of serum molecular forms of inhibin (A and B) could be useful for the diagnosis, prognosis and follow-up of placental tumours.

METHODS

A total of 17 patients with hydatidiform mole (n = 13), invasive mole (n = 1) or choriocarcinoma (n = 3) were studied; serum concentrations of inhibins A and B, human chorionic gonadotrophin (HCG) and its free beta subunit (HCGbeta) were measured before chemotherapy (after mole evacuation for eight patients) and also during the course of chemotherapy (for 10 patients).

RESULTS

After evacuation or before chemotherapy for refractory disease, serum inhibin A and B concentrations were found to be increased in 10/17 and 4/17 patients, when HCG and HCGbeta were high in all patients. In 10 patients with a follow-up during treatment, nine had a high concentration of inhibin A which correlated with those of HCG and HCGbeta. Normalization of inhibin A was faster than that of HCG and HCGbeta for three and six patients respectively. There was no correlation between changes of inhibin B and HCGbeta concentrations.

CONCLUSIONS

Our results suggest that inhibins A and B are not useful markers and that HCG determination still remains the most useful marker for diagnosis and follow-up of placental tumours.

Concentration of free hCGbeta subunit in serum as a prognostic marker for squamous-cell carcinoma of the oral cavity and oropharynx

This study was conducted to evaluate the clinical usefulness of serum hCGbeta in the diagnosis and prognosis of patients (n = 59) with cancers of the oral cavity and oropharynx. As a reference marker we used squamous-cell carcinoma antigen (SCCAg). A blood sample was obtained from all patients before primary surgery. Serum hCGbeta was determined by a time-resolved immunofluorometric assay (IFMA) and SCCAg by a solid phase immunoenzymometric assay. Elevated preoperative hCGbeta levels were observed in 8 (14%) and elevated SCCAg in 12 (20%) out of 59 patients. Patients with preoperatively elevated hCGbeta had a shorter recurrence-free survival when compared with those with normal hCGbeta levels (log-rank Chi-squared = 6.83, p =.009), and the risk-ratio for recurrence during follow-up for those was 3.6 (95% CI = 1.29-9.94). In a Cox multivariate model hCGbeta (p = 0.039) and stage (p = 0.044) were independent prognostic factors. SCCAg showed no correlation with recurrence-free survival. We conclude that determination of hCGbeta in serum is a potential marker in the prognostic evaluation of patients with SCC of the oral cavity and oropharynx.

Immunoassay of human chorionic gonadotropin, its free subunits, and metabolites

Multiple hCG-related molecules are present in pregnancy serum and urine samples. These include nonnicked hCG (the hormone), nicked hCG, hyper- and hypoglycosylated hCG, hCG missing the C-terminal extension, free α-subunit, large free α-subunit, free β-subunit, nicked free β-subunit, and β-core fragment. Over 100 immunoassays are sold for quantifying hCG-related molecules in serum or urine. Each measures nonnicked hCG and one of seven combinations of the other hCG-related molecules. This is the source of interassay discordance in hCG determinations. Whereas minor variations are noted in different kit results in normal pregnancy samples (more than twofold variation), much larger variations may be found in two immunoassay results in irregular gestations (spontaneous abortion, aneuploidy, preeclampsia, cancers, and trophoblast disease). Care is needed in choosing an immunoassay. What the assay measures may be more important than its cost or speed. This article reviews the structure of hCG and related molecules. It examines the stability and degradation of hCG, and recognition of hCG-related molecules by different types of immunoassay. Also reviewed are new assays for specifically detecting these other hCG-related molecules.

Disappearance of human chorionic gonadotropin and its α- and β-subunits after term pregnancy

We have used high-specificity and precision immunofluorometric assays to measure the elimination half-times of human chorionic gonadotropin (hCG), hCGα, and hCGβ in serum over 21 days after delivery in six women with term pregnancies. Baseline concentrations and half-times were calculated with the use of a curve-fitting algorithm for multiexponential decay. In contrast to the two-component model, a three-component exponential function with baseline provided a fit for which predicted values could not be distinguished from the observed values by analysis of variance. Median half-times were 3.6, 18.0, and 53.0 h for hCG; 1.0, 23.4, and 194 h for hCGβ; and 0.6, 6.2, and 21.9 h for hCGα. The mean ratio of hCGα to hCG decreased rapidly from 36.9% to 3.3% on day 3; thereafter it increased to 64.3% 21 days after delivery because of a higher baseline concentration of hCGα. hCGβ had the slowest total elimination rate, and the ratio of hCGβ to hCG in serum increased from 0.8% before delivery to 26.7% after 21 days. If the metabolism of hCG and hCGβ is similar in patients with trophoblastic disease, the ratio of hCGβ to hCG must be evaluated with caution in samples taken several days after initiating therapy. We conclude that the disappearance of hCGβ from plasma is slower than previously recognized and that the ratios of hCGβ or hCGα to intact hCG vary as a function of postpartum time. Such information may be important in clinical studies of pregnancy disorders.

Pathophysiological importance of various molecular forms of human choriogonadotropin

Human chorionic gonadotropin (hCG), its subunits and fragments are widely used for diagnostic purposes. In addition to the diagnosis of pregnancy and pregnancy related disorders, hCG determinations are used for diagnosis of trophoblastic and recently also nontrophoblastic tumors. The use for diagnosis of nontrophoblastic tumors requires highly specific and ultrasensitive assays. With these, it is possible to measure the concentrations of both hCG, the free beta-subunits and the so called beta-core fragment in healthy subjects. Therefore it is important to establish reference values for these and also to be aware of the influence of physiological factors on the serum and urine concentrations. Improved standardization of the assay methods is also essential for these novel applications of hCG determinations to become useful.

Different hCG assays to measure ectopic hCG secretion in bladder carcinoma patients

We evaluated the clinical performance of assays measuring intact human chorionic gonadotropin alone (i-hCG), intact and nicked human chorionic gonadotropin (i-hCG and hCGn), free beta-subunit (free beta-hCG) and total beta-human chorionic gonadotropin (t-hCG) using different commercial kits, in a group of bladder carcinoma patients with ectopic human chorionic gonadotropin (hCG) secretion, at diagnosis and during treatment. The diagnostic sensitivity obtained ranged between 63.6% and 75.7% (t-hCG assays), 72.7% (free beta-hCG assay), 18.2% (i-hCG and hCGn) and 6% (i-hCG assay). Median increases of hCG during treatment in patients with chemotherapy resistance ranged from 4.9 to 6.9 for t-hCG and free beta-hCG assays and from 1.4 to 3.2 for i-hCG and i-hCG plus hCGn assays. Median decreases when chemotherapy was efficient ranged from 2.8 to 3.3 (t-hCG and free beta-hCG assays) and from 1.1 to 1.5 (i-hCG and i-hCG plus hCGn assays). We conclude that t-hCG and free beta-hCG are the most suitable assays for the management of bladder carcinoma patients as the ectopic secretion of chorionic gonadotropin is mainly due to the free beta-subunit.

Tumorigenesis and metastasis of neoplastic Kaposi's sarcoma cell line in immunodeficient mice blocked by a human pregnancy hormone

Kaposi's sarcoma (KS) occurs more often in men than in women and HIV-1-associated KS has a high occurrence in homosexual men (over 30%). Most cultures of KS tumours yield cells with properties of hyperplastic (not malignant) endothelial cells under the control of several cytokines. The role of HIV-1 may be in promoting high levels of some cytokines and providing stimulation to angiogenesis by the HIV-1 Tat protein, which synergizes with basic fibroblast growth factor in promoting these effects. Here we describe an immortalized AIDS-KS cell line (KS Y-1) and show that these cells produce malignant metastatic tumours in nude mice and are killed in vitro and in vivo (apparently by apoptosis) by a pregnancy hormone, the beta-chain of human chorionic gonadotropin. Similarly, chorionic gonadotropin kills KS SLK, cells from another neoplastic cell line (established from a non-HIV-associated KS), as well as the hyperplastic KS cells from clinical specimens grown in short-term culture, but does not kill normal endothelial cells. These results provide evidence that KS can evolve into a malignancy and have implications for the hormonal treatment of this tumour.

Inhibin as a marker for hydatidiform mole: a comparative study with the determinations of intact human chorionic gonadotrophin and its free beta-subunit

OBJECTIVE

The purpose of the study was to evaluate plasma inhibin as a marker of hydatidiform mole and to compare the results with intact human chorionic gonadotrophin (hCG) and its free beta-subunit.

DESIGN

Serial determinations of the plasma concentrations of inhibin, intact human chorionic gonadotrophin and its free beta-subunit in cases of hydatidiform mole over an average period of 140 days.

PATIENTS

Five cases of hydatidiform mole, including patients with spontaneous remission after evacuation or persistent trophoblastic disease.

MEASUREMENTS

Immunoreactive inhibin, hCG and free hCG beta-subunit were measured using standard enzyme immunoassays.

RESULTS

Inhibin and free hCG beta-subunit levels were greater than in normal pregnant women at the same gestational age. Only intact hCG could detect the persistence of trophoblastic tissue.

CONCLUSIONS

Our data suggest that inhibin, intact human chorionic gonadotrophin and free beta-subunit might be useful as diagnostic markers of molar pregnancies. However, the original method of intact hCG determination is still superior for follow-up.

Flow cytometry method for the analysis of membrane-associated human chorionic gonadotropin, its subunits, and fragments on human cancer cells

A quantitative flow cytometry method for the analysis of membrane-associated human chorionic gonadotropin (hCG), its subunits, and fragments on human cancer cells was developed using a double-antibody reaction; a flow cytometry with a 2-W argon laser, standard settings, and filters for fluorescein isothiocyanate use; commercially available software; and the ectopic hCG producer CCL 2 HeLa cells from the American Type Culture Collection (ATCC) as a cell control to standardize the reagents and for overall quality control. Twenty-two monoclonal antibodies (MoAb) and immunoglobulin G fractions from three rabbit polyclonal antisera were tested for effects of antibody concentration (titration), reproducibility at different levels of epitope expression, and variability of epitope expression to select appropriate primary antibodies. Based on the results of the various tests, three polyclonal immunoglobulin G antibodies and a panel of nine MoAb directed to epitopes located in five different regions on the hCG molecule were selected as first antibodies. Their specificity was determined by using two unrelated MoAb of the same isotype at the same concentration to replace the primary MoAb and by a competition experiment. The unrelated MoAb also were used for the selection of the appropriate control fluorescence profile needed for the software. The unique characteristics of this method were: the use of living cells, standardized reagents, internal and external quality control, and the highest sensitivity, which could detect as few as 10(3) molecules of fluorochrome per cell. Serial analyses of the ATCC CCL 2 HeLa cells and two of its variants and of the eutopic hCG producer JEG-3 choriocarcinoma cells revealed the expression of membrane-associated epitopes of intact hCG, its subunits, and fragments by a high percentage of the cells, indicating that the expression of these sialoglycoproteins by these two different types of cancer cells is a common phenotypic characteristic.

Gestational trophoblastic disease: what have we learned in the past decade?

Hydatidiform moles can be classified into two distinct entities: complete and partial. Complete moles are androgenetically derived, are characterized by a predominance of the 46,XX karyotype, and are associated with a significantly higher incidence of malignant sequelae than are partial moles. A subset of complete moles resulting from dispermy are heterozygous (46,XY) and appear to be associated with the greatest risk of malignancy. Free subunits of human chorionic gonadotropin, beta core fragments, and acidic variants of human chorionic gonadotropin can now be readily measured by radioimmunoassays, fluoroimmunoassays, or isoelectric focusing techniques. Determination of these markers can be of value not only in monitoring response to therapy, but also as prognostic indicators. A subgroup of patients, traditionally classified as "high risk" or poor prognosis, who show poor responses to conventional combination chemotherapy have recently been designated as "ultra-high-risk" patients. They require more complex chemotherapy and possibly surgery and radiotherapy to achieve remission. The development of chemotherapy over the past decade, including the introduction of etoposide and cisplatin into current protocols and the treatment of patients with advanced gestational trophoblastic disease, are considered in this review.