Human Chorionic Gonadotropin Assays Research Articles

Design and implementation of a low‐cost portable reader for thermometric lateral flow immunoassay

AbstractLateral flow immunoassay (LFIA) is a widely used tool for point‐of‐care testing (POCT). Although the method is fast and inexpensive, it provides only qualitative or semi‐quantitative information, which limits the scope of its applications in POCT. Here, we report the development of a low‐cost, portable LFIA reader based on photothermal detection of reporters (such as colloidal gold and colored latex beads) captured on LFIA strips using a low‐power green laser as the heating source and a single‐element infrared sensor as the detector. For 40‐nm colloidal gold, we measured a detection limit of 3 × 105 particles/mm2 by laser irradiation of the reporters at 532 nm with an intensity of 20 W/cm2. The photothermal detection enables a 10‐fold enhancement in sensitivity over color visualization with the naked eye. More importantly, with the use of the control line intensities as internal calibrants, the results so obtained are quantitative and useful to support critical decision‐making in POCT, as demonstrated by gold‐based assays for human chorionic gonadotropin and human immunodeficiency virus as well as latex‐based assays for nucleocapsid protein of the SARS‐CoV‐2 virus.

An enzyme immunoassay to determine human chorionic gonadotropin (HCG) in serum and urine samples using an ultra-microanalytical system

The determination of Human Chorionic Gonadotropin (HCG) in biological fluids is of great interest in the early pregnancy diagnostics, the evaluation of pregnancy disorders, as a tumor marker, as a screening procedure for anti-doping control, and many other purposes. A simple sandwich-type UltraMicro Enzyme-Linked ImmunoSorbent Assay (UMELISA) has been developed for the measurement of HCG in serum and urine samples. Strips coated with a high affinity MAb directed against HCG are used as solid phase, to ensure the specificity of the assay. The HCG assay was completed in 1.5 h, with a measuring range of 0.76–400 mIU/mL. The intra- and inter-assay coefficients of variation were lower than 10 %, depending on the HCG concentrations evaluated. Recovery percentages were 96.43–97.16 % (serum) and 98.10–99.04 % (urine). The assay detected intact HCG, nicked HCG, HCG β, and nicked HCG β, and did not recognize any of the interfering molecules tested. Regression analysis showed a good correlation with Elecsys in serum (n = 1459, r = 0.952, ρc = 0.948) and urine (n = 869, r = 0.988, ρc = 0.978). A good correlation was also found with 84 RIQAS samples analyzed with the kits Elecsys (r = 0.969, ρc = 0.957), Architect (r = 0.982, ρc = 0.970), Dimension (r = 0.989, ρc = 0.977), and Bioscience (r = 0.992, ρc = 0.980), all with a p < 0.01. Comparison with transvaginal ultrasonography in early pregnancy detection showed a specificity and a sensitivity of 100 % (n = 2385, κ = 1). The analytical performance characteristics of UMELISA HCG endorse its use for the quantification of HCG in serum and urine samples. This assay will make a cost-effective diagnostic kit accessible to low-income countries and is now available in the Cuban Public Health System.

ROLE OF DAY 4 AND DAY 7 Β-HCG AS AN EARLY PREDICTOR OF SUCCESS AFTER METHOTREXATE THERAPY FOR TUBAL ECTOPIC PREGNANCIES

Background: Tubal ectopic pregnancy is potentially life-threatening with an estimated incidence of 1% to 2% of all pregnancies with the wide availability of transvaginal ultrasound and quantitative serum beta human chorionic gonadotropin (β-hCG) assay; ectopic pregnancies can be diagnosed early, leading to successful management without resort to surgery. Objective: Evaluation of β-hCG levels between days 4 and 7 as a predictor of methotrexate therapy success for ectopic pregnancy. Patients and Methods: 50 cases, diagnosed of ectopic pregnancy, This study was carried out on Al-Hussein Hospital during July 2018 and August 2019 All cases were subjected to full history taking, complete clinical examination, ultrasongraphy and Laboratory investigations as Complete blood count, Liver profile (ALT and AST), Serum creatinine, and Serum β-hCG levels on day1, 4, and7 after methotrexate therapy. Results: The mean age was 28 ± 5 years, ranging between 20 and 40 years. The average gestational age was 5 weeks, while the average parity was 1. Of 50 cases, 36 patients (72%) succeeded and 14 failed. The ROC curve for the hCG index identified an hCG index value of 0.192 (19% decrease of hCG value between day 1 and day 4) as the best predictor for ectopic pregnancy treated successfully with a single dose of methotrexate. Sensitivity for the test was 80% and accuracy was 75%. Conclusion: Early serum β-hCG decline is associated with a very high probability of treatment success. However, given that we found an 80% success rate, not 100%, we suggest it is prudent to continue the serial monitoring of serum β-hCG until the complete resolution of the ectopic pregnancy.

Human Chorionic Gonadotropin Assay in Cervicovaginal Secretions as a Predictor of Preterm Delivary

Preterm birth (PTB) is defined as birth before 37 weeks’ gestation, accounts for 6–10% of all births and is a major contributor to neonatal and infant morbidity and mortality The aim of the current study is to assess the diagnostic accuracy of Beta-subunit of human chorionic gonadotropin (β-HCG) in cervico-vaginal secretion, as a biochemical predictor of preterm labor. A cross sectional study was conducted on(100) women between 24th -36th week of singleton pregnancy. The gestational age was determined by the first day of last menstrual period and confirmed by ultrasound, cervi-covaginal secretion samples was obtained through speculum examination from all the patient, the swab disposed of the sample was quantitatively tested for the level of beta-HCG, the level of beta HCG was measured by the radioimmunoassay method using a commercial kit, and the result was reported in milli-international units per milliliter, the results revealed that there was significant difference between both groups regarding S/D ratio of beta HCG (66.97- 21.45) as range S/D for preterm group was higher than full term group the qualitative test was found to have sensitivity, specificity, PPV, NPV and diagnostic accuracy to predict PTB of 68.33%, 96.06%, 75.93%, 94.35% and 91.79%,respectively, It was found to be more sensitive in the high-risk patients, but more specific in the low risk control group.

Gold nanoparticle-decorated metal organic frameworks on immunochromatographic assay for human chorionic gonadotropin detection.

Gold nanoparticle-decorated metal organic frameworks (MOF@AuNPs) with significantly enhanced color signal intensity were synthesized through in situ growth of AuNPs on the MOF skeleton. The resultant MOF@AuNP nanocomposites were characterized with 16.7-fold higher absorbance than conventional 40nm AuNPs (AuNP40). Thus, for the first time, we applied it as a signal amplification label to improve the immunochromatographic assay (ICA) of human chorionic gonadotropin (HCG). The detection limit of our enhanced ICA was 1.69 mIU/mL, which is ca. 10.6-fold improvement in sensitivity compared to traditional AuNP40-ICA. The recoveries of this MOF@AuNPs-ICA ranged from 86.03 to 119.22%, with coefficients of variation of 3.05 to 13.74%. The reliability and practicability were further validated by the clinically used chemiluminescence immunoassay method. Given their excellent signal amplification ability, the proposed MOF@AuNPs could serve as an ideal ICA label for rapid and sensitive detection of disease biomarkers. Graphical abstract.

A step forward in identifying the right human chorionic gonadotropin assay for testicular cancer.

Clinical practice guidelines for the management of germ cell tumors recommend the measurements of human chorionic gonadotropin (hCG) and/or free hCGβ subunit for earlier diagnosis/recognition of the residual disease, for the prognostic evaluation and for the post-chemotherapy surveillance. However, the marketed hCG assays are validated and approved only for pregnancy purposes, with the sole exception of the Elecsys 'hCG+β' assay (Roche Diagnostics), cleared in Europe for oncological application. Theoretically, the hCG assay design for oncological purposes should fulfil the recommendations of the International Society of Oncology and Biomarkers requiring the use of antibodies displaying an equimolar recognition of both intact hCG and hCGβ monomer. Further analytical requirements should also be considered, such as optimal analytical sensitivity to allow an early tumor detection and low cross-reactivity for luteinizing hormone (LH). For the Elecsys assay, the detection limit (0.2 U/L) and the reported cross-reactivity for LH (0.12%) may be considered adequate if compared with the recommended requirements. Another issue is the definition of decision limits for oncologic purposes. After 3 years of clinical experience using the Elecsys assay in the oncology setting, we were able to define limits partitioned by sex and age as follows: males <50 years, 0.3 U/L; males >50 years, 2.3 U/L; female <50 years, 2.1 U/L; female >50 years, 5.6 U/L. There is an urgent need to disseminate appropriate educational information and to boost the clinical use of selective, highly sensitive and precise assays, specifically manufactured for cancer application.

Complete hydatidiform mole with a twin pregnancy at 26 weeks: a rare obstetric complication.

Complete hydatidiform mole with a twin pregnancy at 26 weeks: a rare obstetric complication.

Human Chorionic Gonadotropin Assays for Testicular Tumors: Closing the Gap between Clinical and Laboratory Practice.

Clinical practice guidelines recommend the measurement of human chorionic gonadotropin (hCG) and/or hCGβ in serum for management of testicular germ cell tumors (GCTs). These guidelines, however, disregard relevant biochemical information on hCG variants to be detected for oncological application. We set out to provide a critical review of the clinical evidence together with a characterization of the selectivity of currently marketed hCG immunoassays, identifying assays suitable for management of GCTs. Evidence sources in the available literature were critically appraised. Most instances of misdiagnosis and mismanagement of testicular GCTs have been associated with hCG results. According to the clinical evidence, 36% of patients with seminoma show an exclusive hCGβ increase, and 71% of patients with nonseminomatous GCTs (NSGCTs) show an increase of intact hCG and/or hCG + hCGβ, whereas the hCGβ increase in NSGCTs is variable according to the tumor stage and histology. hCG + hCGβ assays that display an equimolar recognition of hCG and hCGβ, or at least do not overtly underestimate hCGβ, may be employed for management of testicular GCTs. Assays that underestimate hCGβ are not recommended for oncological application. In addition to the hCG + hCGβ assay in service, an additional assay with broader selectivity for other hCG variants should be considered when false-negative or false-positive results are suspected on the basis of clinical data.

Use of beta subunit of human chorionic gonadotropin assay as a diagnostic tool for prelabor rupture of membranes

Purpose: The study aimed at assessment of the accuracy of the β-hCG test in vaginal washing fluid for diagnosis of prelabor rupture of membranes (PROM).Patients and methods: Two groups of pregnant women from 17 to 38 weeks of gestation were recruited. The first group (PROM group) included 50 pregnant women with unequivocal PROM. The other group included 50 pregnant women with intact membranes. A sterile speculum examination was performed. If less than 5 cc was collected or no fluid found, 10 cc sterile saline was sprinkled on the vaginal wall and 5 cc were recollected in a sterile syringe. Two drops of collected fluid were used for qualitative testing of β-hCG. The remaining fluid was used for quantitative assessment of β-hCG.Results: The quantitative β-hCG test results were significantly higher in PROM group (median and range: 138.5 (23–475) versus 13 (1–55); the difference in medians and 95% CI: 105 (91–166); p value: <.001). The qualitative β-hCG test was positive in 42/50 (84%) of the PROM group, while it was negative in 50/50 (100%) of the intact membranes group. Areas under receiver operating characteristics (AUC) for both the quantitative and qualitative β-hCG tests were high (0.97, 95% CI: 0.91–0.99, p value: <.001 and .92, 95% CI: 0.84–0.96, p value: <.001, respectively). The suggested cut-off of β-hCG for the quantitative test was 32 mIU/ml. The sensitivity of quantitative and qualitative tests are: 94, 95% CI: 83.5–98.7% and 84, 95% CI: 70.9–92.8%, respectively. The specificity of quantitative and qualitative tests are: 94, 95% CI: 83.5–98.7% and 100, 95% CI: 92.9–100%, respectively.Conclusion: β-hCG test (either quantitative or qualitative) in vaginal washing fluid can be used in the diagnosis of PROM in both preterm and term cases.

Laser-fabricated gold nanoparticles for lateral flow immunoassays

Gold nanoparticles fabricated by pulsed laser ablation are an attractive alternative over those made by chemical reduction, as they offer a more reactive, chemically-bare surface. In this manuscript, we investigate the interactions of these nanoparticles with different classes of antibodies and quantify surface coverage via a fluorescence-based displacement assay. Saturation surface coverage of monoclonal antibodies was found to be almost 2× higher for particles made by pulsed laser ablation (∼28 antibodies/particle) as opposed to those made by chemical means (∼17 antibodies/particle). This higher coverage translated into ∼2× better immunoassay sensitivity, demonstrated by a sandwich lateral flow assay for human chorionic gonadotropin. This work highlights the advantages of these pulsed laser-fabricated materials and showcases their unique properties for colorimetric assay development.

Clinical Analysis of Ectopic Pregnancies in a Tertiary Care Centre in Southern India: A Six-Year Retrospective Study.

Ectopic Pregnancy (EP) is a life-threatening emergency commonly encountered by medical practitioners where diagnosis can often be missed. Any woman in the reproductive age group, presenting with lower abdominal pain or vaginal bleeding must raise the suspicion of an ectopic pregnancy to prevent mortality and morbidity. To review all cases of EP and determine the incidence of EP. To study the high risk factors and know the types of clinical presentation, methods of diagnosis, outcome and complications. This was a retrospective cohort study, conducted at a tertiary care medical teaching hospital in Pondicherry, India. Medical records of all women with an EP between 2009 and 2015 were retrieved. Demographic data, parity, risk factors, clinical features, mode of management and need for blood transfusion was noted. Main outcome measures studied were the incidence of EP, risk factors, mortality and morbidity in these women. Data was entered in Microsoft Excel spreadsheet and analysed using SPSS software version 19.0. For categorical variables, data was compiled as frequency and percent. For continuous variables, data was calculated as mean ± SD. Seventy-two EP were diagnosed during the six-year period with an incidence of 9.1/1000 pregnancies. Majority of women were aged 21-30years (51.39%), 27.8% women were nulliparous. The most common risk factors were previous abortion (36.1%) and pelvic surgery (37.50%). Fifteen cases (20.8%) were diagnosed in women who had tubectomy. The classic triad of lower abdominal pain, amenorrhoea and vaginal bleeding was seen in 29(40.3%) cases. Ultrasonography was required to arrive at a diagnosis in 28(38.9%) cases. Urine pregnancy test was positive in 100% of cases. Majority (94.4%) were tubal ectopic pregnancies. Medical management with methotrexate alone benefitted 10(13.89%) of patients while another four required surgery for failed medical management. More than half of the patients (59.7%) required blood transfusion and two (2.8%) had transfusion related acute lung injury. No deaths were noted. Common risk factors for EP must be identified. Use of transvaginal ultrasonography and human chorionic gonadotropin assay have revolutionised the management of EP and serve as valuable adjuncts to early diagnosis and management.

Human chorionic gonadotropin cutoff value determined by receiver operating characteristic curve analysis is useful but not absolute for determining pregnancy outcomes

Abstract Objective: To assess the clinical value of a single early human chorionic gonadotropin (HCG) assay (day 14 post embryo transfer) in assisted reproductive technology (ART) pregnancies. Design: Retrospective study. Settings: The Assisted Reproductive Unit at Jordan University Hospital, Amman, Jordan. Patients: During 2009–2011, a total of 248 embryo transfer cycles resulting in pregnancy, defined as serum HCG concentration of ⩾10 IU/l, were included. Interventions: None. Materials and methods: Pregnancies were classified as viable (live fetus at 24 weeks gestation) or non-viable (biochemical pregnancy, miscarriage, ectopic pregnancy). Receiver operating characteristic (ROC) curve analysis was used to evaluate the cutoff value of HCG with maximal sensitivity and specificity to differentiate between viable and non-viable pregnancies. Results: The median HCG concentration was 264 IU/l in viable pregnancies and 120 IU/l in non-viable pregnancies ( p p Conclusion: HCG cutoff values determined by a ROC curve analysis are useful but not absolute for discriminating between viable and non-viable pregnancy outcomes on day 14 after embryo transfer. So it is important to continue routine monitoring of ART pregnancy outcomes.

Gestational Trophoblastic Neoplasia: Experience from a Tertiary Care Center of India.

Gestational trophoblastic neoplasia (GTN) comprise a spectrum of interrelated conditions originating from the placenta. With sensitive assays for human chorionic gonadotropin (β-hCG) and current approaches to chemotherapy, most women with GTN can be cured with preservation of reproductive potential. The purpose of this analysis was to address the outcome of GTN in patients from a tertiary care center of India. We undertook a retrospective and prospective review of GTN cases treated at our center over a period of 7 years from 2008 to 2014. Patients of GTN were assigned to low-risk or high-risk categories as per the FIGO scoring system. The low-risk group was treated with combination of actinomycin-D and methotrexate and the high-risk group received the Etoposide, Methotrexate, Actinomycin-D/ Cyclophosphamide, Vincristine (EMA/CO) regimen. Salvage therapy was Etoposide, Paclitaxel /Paclitaxel, Cisplatin (EP/TP). Treatment was continued for three cycles after normalization of β-hCG level, after which the patients were followed up regularly. In total, 41 GTN patients were treated at our institution during the above period; 17 were in the low-risk and 24 were in the high-risk category. The lung was the most common site of metastasis. All low-risk patients achieved complete remission. Among high-risk patients, one patient died while receiving first cycle chemotherapy, one patient relapsed, and 22 patients achieved complete remission. The single relapsed patient also achieved remission with second-line chemotherapy. Risk-stratified treatment of GTN was associated with acceptable toxicity and resulted in outcome that was comparable with international standards. The use of two-drug combination in low-risk patients is a better option especially in developing countries.

Outcome of Gestational Trophoblastic Neoplasia: Experience from a Tertiary Cancer Centre in India

AimsGestational trophoblastic neoplasms (GTN) comprise a spectrum of interrelated conditions originating from the placenta. With sensitive assays for human chorionic gonadotropin (β-hCG) and current approaches to chemotherapy, most women with GTN can be cured with preservation of reproductive potential. The purpose of this analysis was to address the outcome of GTN from a developing country, as data are largely sparse from this region. Materials and methodsWe undertook a retrospective review of GTN cases treated at our centre from 2001 to 2008. Patients of GTN were assigned to low-risk (score ≤ 6) or high-risk (score ≥ 7) categories as per the modified World Health Organization scoring system. The low-risk group was treated with single-agent methotrexate (MTX) and the high-risk group received the EMA/CO regimen. Salvage therapies were EMA/EP or BEP. Treatment was continued until serum β-hCG values were normal for three consecutive chemotherapy cycles, after which the patients were kept on follow-up. ResultsIn total, 70 GTN patients were treated at our institution during this period; 48 (68%) were low-risk and 22 (32%) were in the high-risk category. The median β-hCG level was 50 000 IU/l. The lung was the most common site of metastasis, seen in 15 (21%) patients. Among 48 low-risk patients, 37 (77%) received chemotherapy, of whom 25 (68%) were treated with MTX and 24 (96%) achieved a complete response. Twelve low-risk patients (32%) received EMA/CO therapy; 10 (83%) achieved a complete response. The 22 high-risk patients received EMA/CO and of these 16 (73%) achieved a complete response, two (9%) progressed, two (9%) died of progressive disease and two (9%) were lost to follow-up. Grade 3/4 toxicities with MTX included mucositis in two (8%) and neutropenia in five (21%) patients. At a median follow-up of 16.6 months, overall survival in the low- and high-risk groups was 100 and 88.8%, respectively. ConclusionRisk-stratified treatment of GTN was associated with acceptable toxicity and resulted in outcome that was comparable with international standards.

The Role of Surgery in the Management of Gestational Trophoblastic Neoplasia

Although sensitive human chorionic gonadotropin assays and advances in chemotherapy have assumed primary importance in the management of gestational trophoblastic neoplasia, surgery remains important in the overall care of these patients. Management of molar pregnancies consists of surgical evacuation and subsequent monitoring. Hysterectomy decreases the risk of post-molar trophoblastic disease in appropriate patients and, when incorporated to primary management of gestational trophoblastic neoplasia, can decrease the chemotherapy requirements of patients with low-risk disease. In patients with high-risk disease, surgical intervention is frequently required to control complications of disease or as therapy to stabilize patients during chemotherapy. Hysterectomy, thoracotomy, or other extirpative procedures may be integrated into the management of patients with chemorefractory disease. Interventional procedures are useful adjuncts to control bleeding from metastases.

APPLICATION OF IMMUNOMAGNETIC PARTICLES TO ENZYME-LINKED IMMUNOSORBENT ASSAY (ELISA) FOR IMPROVEMENT OF DETECTION SENSITIVITY OF HCG

This investigation was aimed at using superparamagnetic particles to enzyme-linked immunosorbent assay (SPIO-ELISA) of human chorionic gonadotropin (hCG) to enhance detection sensitivity of hCG. We found that N-(3-dimethyl aminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) was the best cross-linking reagent to link anti hCG α antibody to superparamagnetic particle (SPIO-anti hCG α antibody immunomagnetic particle). To improve the specificity of the assay, a horse radish peroxidase (HRP)-labeled anti-hCG beta monoclonal antibody was used to detect captured hCG using double antibody sandwich ELISA assay. SPIO-ELISA application to determine hCG increased the sensitivity to 1 mIU/mL, which is a level of sensitivity enabling the diagnosis of pregnancy during the early gestational period.

Magnetic particle-linked anti hCG β antibody for immunoassay of human chorionic gonadotropin (hCG), potential application to early pregnancy diagnosis

The objective of this study was to develop a magnetic particle-linked monoclonal antibody to hCG β for immunosorbent assay of human chorionic gonadotropin (hCG) with improved detection sensitivity. Monoclonal antibody against hCG β was found to be optimally cross-linked to the superparamagnetic particles (SPIO) using EDC and NHS as cross-linking reagents. This superparamagnetic particle-linked monoclonal antibody was able to concentrate hCG from a tested solution for further ELISA assay using horse radish peroxidase-labeled monoclonal antibody against hCG β. This hybrid technique had greatly decreased the detection limit to 0.1mIU/mL, making an early detection of pregnancy possible. With an improved sensitivity and simple operation, the magnetic particle-linked anti hCG β antibody for immunoassay of human chorionic gonadotropin (hCG) has a great potential to supersede the traditional ELISA for pregnancy diagnosis.

Ectopic pregnancy after infertility treatment

Early pregnancy complications are more common in women who conceive after infertility treatment. Most of these occur before 12 weeks of gestation and include miscarriage, vaginal bleeding, intrauterine hematoma, vanishing twin, and ectopic pregnancy (EP). The incidence of EPs following infertility treatment is much higher compared with that in spontaneous pregnancies. The occurrence of an EP is very distressing to an infertile couple, who has lots of hopes pinned on the treatment outcome, especially because of the cost incurred and the physical and mental trauma both have gone through during the treatment process. The association between infertility and EP is complex, as it can be a consequence of infertility as well as a cause. The two principal risk factors for an EP are genital tract infections and tubal surgeries. Though several etiologies are proposed, but patients with tubal factor infertility are at an increased risk of an EP. Earlier diagnosis of EP helps to improve prognosis and optimize subsequent fertility. It is pivotal to evaluate the likelihood of subsequent occurrence of an EP and be too vigilant when treating. The correct choice of the treatment modality should be made to prevent the recurrence. The early prediction of the pregnancy outcome therefore has great importance for both the couple and clinician. Today with the help of sensitive beta human chorionic gonadotropin (β-hCG) assays and transvaginal sonography, one can diagnose an EP prior to symptoms, and conservative treatment for the preservation of the fallopian tube is possible. Conservative management in the form of expectant and medical management should be considered as a first-line treatment modality, provided that the overall clinical picture suggests that it is safe to do so. If not, laparoscopic management of EPs appears to be the favored approach of management as compared to laparotomy.

Label-free amperometric immunosensor for the detection of human serum chorionic gonadotropin based on nanoporous gold and graphene

A label-free amperometric immunosensor for fast and sensitive assay of human serum chorionic gonadotropin (hCG) is presented. hCG was immobilized on nanoporous gold (NPG) foils and using hydroquinone (HQ) redox species as indicator. The variation of amperometric response to the concentration of hCG, the target antigen, was evaluated by cyclic voltammetry in phosphate-buffered solution. Taking advantage of dual-amplification effects of the NPG foils and graphene sheets (GSs), the immunosensor exhibited a specific response to hCG in the range of 0.5–40.00 ng ml −1 with a detection limit of 0.034 ng ml −1 under optimal conditions. It was demonstrated that our proposed method possesses good accuracy, acceptable precision, and reproducibility. The NPG showed a better sensitizing effect and stability as immobilization matrices.

Comparison of 2 Human Chorionic Gonadotropin Assays as Tumor Markers Assays

To the Editor: Intact human chorionic gonadotropin (hCG), hyperglycosylated hCG, and the free β subunit are the forms of hCG produced by healthy tissues and tumors (1). Intact hCG is the predominant form in serum and plasma in pregnancy and trophoblastic disease, hyperglycosylated hCG in choriocarcinoma and testicular cancer, and the free β subunit in nongestational malignancy. Proteases present in macrophages associated with tumors or present in serum degrade these forms, resulting initially in nicked intact hCG, nicked hyperglycosylated hCG, and nicked free β subunit. Nicked intact hCG rapidly dissociates into free nicked β subunit and free α subunit. The C-terminal peptide is cleaved, and further degradation results in the β-subunit core fragment (1). All of these variants may be present in serum and urine, and an ideal hCG tumor marker assay would detect all of these products. Tumors that produce only free β subunits can be most effectively detected by assays that specifically measure …