Fully automated chemiluminometric assay for hyperglycosylated human chorionic gonadotropin (invasive trophoblast antigen)

Early detection of pregnancy after IVF and embryo transfer with hyperglycosylated HCG versus Elecsys HCG+β assay

RESEARCH QUESTION

Is measurement of hyperglycosylated HCG (hHCG) superior to beta-HCG (HCG+β) for early pregnancy detection after IVF and embryo transfer?

DESIGN

Blood samples were collected on day 4 (+1), 7 (+1) and 11 (+2) after embryo transfer from women aged 18-45 years undergoing first or second fresh or frozen IVF embryo transfer cycles. Biochemical pregnancy was assessed on-site by HCG determination on day 11; clinical pregnancy was assessed by ultrasound on day 21 (+4/-3). Serum hHCG (immunochemiluminometric assay) and HCG+β (Elecsys® HCG+β assay) concentrations were measured. Performance of hHCG and HCG+β for predicting pregnancy was evaluated and cut-offs selected.

RESULTS

In total, 155 women were enrolled and underwent IVF and embryo transfer. Area under the curve (AUC) (95% CI) on day 4 was not significantly different for hHCG (AUC 0.88; 95% CI 0.83 to 0.94) and HCG+β (AUC 0.90; 95% CI 0.84 to 0.95), as was predictive performance on day 7 and 11, with higher AUC estimates compared with day 4. Applying cut-offs derived according to Youden's index on day 4 (hHCG, 100 pg/ml; HCG+β, 1.30 mIU/ml), both biomarkers demonstrated high negative predictive values for ruling out pregnancy (hHCG, 83.8%; HCG+β, 82.8%) and high positive predictive values for ruling in pregnancy (hHCG, 89.0%; HCG+β, 84.9%) on day 21. Diagnostic performance improved from day 4 to day 11.

CONCLUSIONS

Predictive performance for early pregnancy post-IVF embryo transfer of day-5 blastocysts was not significantly different for hHCG and HCG+β; hHCG superiority over HCG+β was not shown.

Reversion of gold nanoparticle aggregates for the detection of Cu2+ and its application in immunoassays

A high concentration of copper is a hazardous element to organisms and human health. Although various strategies have been reported for the sensitive detection of copper, a facile and rapid detection of aqueous copper has seldom been addressed to date. Here, we present an easy and accessible colorimetric method to detect Cu²⁺ using the redispersion of cysteamine-modified gold nanoparticles (CA-AuNPs). Initially, CA caused the aggregation of AuNPs due to the electrostatic interaction and aggregated AuNPs can be regenerated in basic medium. The subsequent addition of Cu²⁺ to the CA-AuNP dispersion could effectively trigger the aggregation of CA-AuNPs, resulting from the coordination reactivity between the deprotonated CA and Cu²⁺. This strategy resulted in a detection limit (LOD) of 1.52 μM in drinking water, which is below the U.S. Environmental Protection Agency permissible limit (20 μM). To demonstrate the broad application of CA-AuNPs, we further applied this method to plasmonic immunoassays based on the competitive interaction of Cu²⁺ between CA-AuNPs and enzymes. The LOD of the Down syndrome biomarker hyperglycosylated human chorionic gonadotropin (H-hCG) was 0.125 mIU mL^-1, which is better than that of commercial immunoassays. Importantly, the determination of H-hCG in serum indicates its applicability for the measurement of real samples. Our assay agrees well with the current immunoassay systems and thus it can easily be expanded to a more common sensing platform for different types of biotargets by changing the corresponding antibodies.

Prospects of electrochemical immunosensors for early diagnosis of preeclampsia

Preeclampsia is a vascular multisystem disorder that accounts for varying degree of morbidity and mortality of mother and the fetus. This can be significantly averted if diagnosed at an early (18-20 weeks) stage of gestation, as there is no known way to prevent preeclampsia. In spite of extensive work on biomarker discovery, the existing method for its detection is mostly based on colorimetric immunoassays whose sensitivity is ranging in nanomolar range. Further, it has also been observed that change in the expression of a single biomarker is not sufficient to diagnose this condition. So, for early diagnosis (by 18-20 weeks), an immuno-diagnostic platform with detection limits in picomolar range and beyond along with the ability to do simultaneous detection of multiple analyte would be of great importance. A nano-immunosensors with an electrochemical readout system can be a potential alternative that promises for the ultrasensitive detection of analyte with high specificity as well as suitability for on-site analysis. Coupling the lateral flow technology with immunosensors would make it feasible to detect more than one biomarker simultaneously on a microchip. This review intends to summarize the potential preeclampsia biomarkers, limitations of existing diagnostic methods along with the recent advancements, and prospects to develop electrochemical immunosensors for early clinical diagnosis.

Hyperglycosylated human chorionic gonadotropin as an early predictor of pregnancy outcomes after in vitro fertilization

OBJECTIVE

To determine whether serum hyperglycosylated human chorionic gonadotropin (hhCG) measured as early as 9 days after egg retrieval can predict ongoing pregnancies after in vitro fertilization and fresh embryo transfer (IVF-ET).

DESIGN

Cohort

SETTING

Academic assisted reproduction center.

PATIENT(S)

Consecutive patients undergoing IVF-ET INTERVENTION(S): Serum hhCG and hCG levels measured 9 (D9) and 16 (D16) days after egg retrieval

MAIN OUTCOME MEASURE(S)

Ongoing pregnancy beyond 9 weeks of gestation.

RESULT(S)

Ongoing pregnancy (62 of 112 participants) was associated with higher D9 levels of hhCG and hCG. However, hhCG was detectable in all D9 OP samples, while hCG was detectable in only 22%. A D9 hhCG level of >110 pg/mL was 96% specific for an ongoing pregnancy, yielding a positive predictive value of 94%. Compared with the D9 hCG levels, hhCG was more sensitive and had a larger area under the curve (0.87 vs. 0.67, respectively). The diagnostic test characteristics were similar between the D16 hhCG and hCG levels.

CONCLUSION(S)

In patients undergoing assisted reproduction, a test to detect pregnancy early and predict outcomes is highly desirable, and hhCG is detectable in serum 9 days after egg retrieval IVF-ET cycles. In this early assessment, hhCG was superior to traditional hCG and highly predictive of ongoing pregnancies.

Human chorionic gonadotropin (hCG) in the secretome of cultured embryos: hyperglycosylated hCG and hCG-free beta subunit are potential markers for infertility management and treatment

Human chorionic gonadotropin (hCG) is produced by trophoblast cells throughout pregnancy, and gene expression studies have indicated that hCG-beta subunit (hCGβ) expression is active at the 2 blastomere stage. Here, we investigated the qualitative hCG output of developing embryos in culture and hCG isoforms expressed in the secretome as a novel sensitive method for detecting hCG. Culture media was collected from the culture plates of 118 embryos in culture (including controls and embryos at different stages of culture) from 16 patients undergoing routine fertility treatment. The hCGβ was detectable in media from 2 pronuclear (2PN) stage embryos through to the blastocyst stage. The hCGβ was absent in 1PN and arrested embryos as well as all media controls. Prior to hatching, hyperglycosylated hCG (hCGh) was observed selectively in 3PN embryos, but after hatching, along with hCG, became the dominant hCG molecule observed. We have reported at the 2PN stage the earliest evidence of hCGβ expression in embryos. There is a suggestion this may be indicative of quality in early embryos, and hCGh seen at the pronuclear stage may suggest triploid abnormality. The dominance of hCG, and hCGh expression, seen after blastocyst hatching may be indicative of potential implantation success. Thus, hCG isoforms have potential roles as biomarkers of embryo viability for embryo/blastocyst transfer.

New discoveries on the biology and detection of human chorionic gonadotropin

Human chorionic gonadotropin (hCG) is a glycoprotein hormone comprising 2 subunits, alpha and beta joined non covalently. While similar in structure to luteinizing hormone (LH), hCG exists in multiple hormonal and non-endocrine agents, rather than as a single molecule like LH and the other glycoprotein hormones. These are regular hCG, hyperglycosylated hCG and the free beta-subunit of hyperglycosylated hCG. For 88 years regular hCG has been known as a promoter of corpus luteal progesterone production, even though this function only explains 3 weeks of a full gestations production of regular hCG. Research in recent years has explained the full gestational production by demonstration of critical functions in trophoblast differentiation and in fetal nutrition through myometrial spiral artery angiogenesis. While regular hCG is made by fused villous syncytiotrophoblast cells, extravillous invasive cytotrophoblast cells make the variant hyperglycosylated hCG. This variant is an autocrine factor, acting on extravillous invasive cytotrophoblast cells to initiate and control invasion as occurs at implantation of pregnancy and the establishment of hemochorial placentation, and malignancy as occurs in invasive hydatidiform mole and choriocarcinoma. Hyperglycosylated hCG inhibits apoptosis in extravillous invasive cytotrophoblast cells promoting cell invasion, growth and malignancy. Other non-trophoblastic malignancies retro-differentiate and produce a hyperglycosylated free beta-subunit of hCG (hCG free beta). This has been shown to be an autocrine factor antagonizing apoptosis furthering cancer cell growth and malignancy. New applications have been demonstrated for total hCG measurements and detection of the 3 hCG variants in pregnancy detection, monitoring pregnancy outcome, determining risk for Down syndrome fetus, predicting preeclampsia, detecting pituitary hCG, detecting and managing gestational trophoblastic diseases, diagnosing quiescent gestational trophoblastic disease, diagnosing placental site trophoblastic tumor, managing testicular germ cell malignancies, and monitoring other human malignancies. There are very few molecules with such wide and varying functions as regular hCG and its variants, and very few tests with such a wide spectrum of clinical applications as total hCG.

Human chorionic gonadotropin measurements in parathyroid carcinoma

OBJECTIVE

Preoperatively, it is difficult to differentiate between parathyroid cancer (PtCa) and severe primary hyperparathyroidism (PHPT) due to a benign tumor. Human chorionic gonadotropin (hCG) is a tumor marker in trophoblastic and nontrophoblastic cancers and hyperglycosylated hCG is increased in hCG-secreting malignancies. We investigated whether hCG can distinguish PtCa cancer from benign disease and add prognostic information.

DESIGN

Observational study.

METHODS

Measurement of urinary hCG (total and malignant isoforms) and serum malignant hCG in 8 subjects with PtCa and in 18 subjects with PHPT (measurement of urine in ten and serum in eight).

RESULTS

Total urinary hCG was normal in the benign PHPT control subjects (range: 0-17 fmol/mg Cr; nl<50). In the PtCa subjects, three had normal total urinary hCG levels and survived complication free for at least 2 years; three had persistently elevated total urinary hCG levels (range: 217-1986 fmol/mg Cr) and sustained hip fracture (n=3) and died (n=2) within 3 and 6 months respectively; two had a rise in total urinary hCG and had hip fracture (n=1) and died (n=2) within 4 and 10 months respectively. Elevated urinary hCG was of the malignant hyperglycosylated isoform. Serum malignant hyperglycosylated hCG values in all of the cancer patients exceeded the maximal serum malignant hCG level of the PHPT subjects with benign disease (3.77 pmol/l).

CONCLUSION

hCG, especially its hyperglycosylated isoform, might add diagnostic and prognostic information in PtCa. Further studies would help to elucidate the role of hCG as a potential tumor marker in this disease.

Serum hyperglycosylated human chorionic gonadotropin to predict the gestational outcome in in vitro fertilization/intracytoplasmic sperm injection pregnancies

Hyperglycosylated human chorionic gonadotropin (H-hCG) is secreted by the placenta in early pregnancy. Decreased H-hCG levels have been associated with abortion in spontaneous pregnancy. We retrospectively measured H-hCG and dimeric hCG in the sera of 87 in vitro fertilization patients obtained in the 3 weeks following embryo transfer and set the results in relation to pregnancy outcome. H-hCG and dimeric hCG were correlated (r(2) = 0.89), and were significantly decreased in biochemical pregnancy (2 microg/l and 18 IU/l, respectively) compared to early pregnancy loss (22 microg/l and 331 IU/l) and ongoing pregnancy (32 microg/l and 353 IU/l). Only H-hCG tended to discriminate between these last two groups.

Aspects of recent development of immunosensors

This chapter focuses on the recent developments in the field of immunosensors. Immunosensors incorporate the specific immunochemical reaction with the modern transducers including electrochemical (potentiometric, conductometric, capacitative, impedance, amperometric), optical (fluorescence, luminescence, refractive index), and microgravimetric transducers. These immunosensor devices with dramatic improvements in the sensitivity and selectivity possess the abilities to investigate the reaction dynamics of antibody–antigen binding and the potential to revolutionize conventional immunoassay techniques. With the rapid development of immunological reagents and detection equipments, immunosensors have allowed an increasing range of analytes to be identified and quantified and in particular, simple-to-use, inexpensive, and reliable immunosensing systems have been developed for areas such as outpatient monitoring, large screening programs, and remote environmental surveillance. Immunosensors with lowered detection limits and increased sensitivities have been developed in various fields, particularly in clinical analysis. A noticeable development trend is also observed in the development of immunosensors combining with other techniques such as flow injection analysis (FIA) or capillary electrophoretic (CE) analysis, which complement and improve the present immunoassay methods. Belov et al. have proposed a novel immunophenotyping method for leukemias which uses a cluster of differentiation antibody microarray, and a microarray of enzyme-linked immunosorbent assay has been developed for autoimmune diagnosis of systematic rheumatic disease. Development of microfluidic immunosensor systems for proteomics and drug discovery have also been reported in recent years where the microfluidic system integrates multiple processes in a single device to improve analytical performance by reducing the reagent consumption and the analysis time, and increasing reliability and sensitivity through automation.

Hyperglycosylated hCG

Hyperglycosylated hCG (hCG-H) is a glycosylation variant of the hormone hCG. Here we review all that is known about this independently functioning molecule. As discussed, it is a very different molecule to the hormone hCG. First, hCG-H is produced by cytotrophoblast cells while regular hCG is made in syncytiotrophoblast cell. Second, it is an autocrine acting directly on the cells which produce it, while regular hCG is an endocrine acting on maternal corpus luteal cells. Third, hCG-H has minimal biological activity in promoting progesterone production compared to regular hCG. Fourth, hCG-H functions unlike regular hCG as an invasion promoter, whether invasion as in choriocarcinoma and testicular germ cell malignancies, or as in implantation of pregnancy. These functions seemingly occur through action on cytotrophoblast cell TGFbeta receptors. Fifth, hCG-H is an essential component for successful human implantation to prevent early pregnancy loss and spontaneous abortion. Sixth, hCG-H is critical for promoting the midtrimester hemochorial implantation, and for preventing preeclampsia. Seventh, measurements of hCG-H have advantages over measurements of regular hCG or total hCG, in detecting pregnancy, pregnancy outcome (failing or term pregnancy), predicting preeclampsia in pregnancy, or as a tumor marker for gestational trophoblastic diseases.

Hyperglycosylated hCG: a variant with separate biological functions to regular hCG

Hyperglycosylated hCG (hCG-H) is an over-glycosylated variant of hCG. While regular hCG is produced by differentiated syncytotrophoblast cells, hCG-H is independently secreted by stem cytotrophoblast cells. hCG-H has an independent function to regular hCG. It is the direct promoter of trophoblast invasion and malignancy. Invasion as in implantation of pregnancy and malignancy as in choriocarcinoma. Neither will occur in the absence of hCG-H. hCG-H measurements have multiple functions. Primarily or exclusively hCG-H is produced at the time of implantation of pregnancy and in the 2 weeks that follows. As such, a good pregnancy test should measure regular hCG and hCG-H equally. This is not commonly the case. Most tests poorly detect hCG-H. New pregnancy tests are needed, including those that measure only hCG-H. Considering that hCG-H is critical for implantation, hCG-H is also invaluable for determining pregnancy outcome and detecting failures. It makes a considerable more accurate test for detecting pregnancy failures and ectopic pregnancies than regular hCG. Down syndrome pregnancies are marked by poor trophoblast differentiation. As such, they are very well marked by using a combination of hCG-H measurements and other screening tests. hCG-H is also an absolute tumor marker for malignant or invasive gestational trophoblastic disease, it can discriminate active and inactive (quiescent) disease, and the need for chemotherapy.

Determination of hyperglycosylated human chorionic gonadotropin produced by malignant gestational trophoblastic neoplasias and male germ cell tumors using a lectin-based immunoassay and surface plasmon resonance

The ability to reliably detect aberrant glycosylation of human chorionic gonadotropin (hCG) may have profound implications for the diagnosis and monitoring of malignant gestational trophoblastic neoplasia, germ cell tumors, other malignancies, and pregnancy complications. To become a clinically useful assay, however, this discrimination of glycoforms should be possible on minimally treated biological specimens. Towards this end, we have developed a lectin-based sandwich-type immunoassay to compare the glycosylation patterns of hCG among urine specimens from patients presenting with a normal pregnancy, invasive mole, choriocarcinoma, and male germ cell tumors using carbohydrate-free antibody fragments as capture reagents and a panel of eight lectins, five recognizing neutral sugars and three recognizing sialic acid. There was no significant difference in the binding of any of the lectins to hCG in the urine of women over the gestational range of 6-38 weeks. Three lectins, however, exhibited differential binding to urinary hCG derived from these normal pregnant controls and that from patients with malignant forms of gestational trophoblastic disease and male germ cell tumors. Galanthus nivalis agglutinin and Maackia amurensis lectin, which bind terminal mannose and alpha(2-3)sialic acid, respectively, preferentially bound pregnancy-derived hCG, whereas the lectin, wheat germ agglutinin, which binds sialic acid and beta(1-4)N-acetylglucosamine, exhibited decreased binding to pregnancy-derived hCG compared to that from patients with male germ cell tumors and malignant gestational trophoblastic neoplasia. The differential binding observed with these three promising lectins is most encouraging and warrants further examination. The experimental paradigm also holds promise for the development of comparable assays for other glycosylated tumor markers.

Hyperglycosylated-hCG (h-hCG) and Down syndrome screening in the first and second trimesters of pregnancy

OBJECTIVE

To validate Down syndrome screening protocols that include hyperglycosylated-hCG (h-hCG) measurements.

METHODS

Measuring h-hCG in 21 641 fresh first- and second-trimester maternal serum samples, but not for clinical interpretation. Nuchal translucency (NT) and pregnancy associated plasma protein-A (PAPP-A) measurements were available in the first trimester; alpha-fetoprotein (AFP), unconjugated estriol (uE3), and human chorionic gonadotropin (hCG) measurements in the second trimester.

RESULTS

Of the 23 first- and 26 second-trimester Down syndrome pregnancies identified, 52 and 65% of h-hCG measurements were above the 95th centile, respectively. At a 3% false positive rate, maternal age, NT, PAPP-A and h-hCG detected 78% of cases (95% CI, 56-93%). Other combinations were consistent with previous modeling utilizing stored samples. A literature summary indicates h-hCG is as strong a marker as free-beta between 10 and 13 weeks' gestation.

CONCLUSIONS

Down syndrome screening performance of h-hCG using fresh samples meets published expectations based on stored samples. h-hCG could replace free beta measurements, at gestational ages as early as 10 weeks.

A single serum test for measuring early pregnancy outcome with high predictive value

OBJECTIVES

Current testing to determine a failing pregnancy requires two separate clinic visits to measure the hCG doubling rate. Diagnosing a failing pregnancy is often done in emergency departments where simplified and accelerated testing methods are needed. Here, we investigated hyperglycosylated hCG (hCG-H) for predicting pregnancy failure.

DESIGN AND METHODS

We studied two independent sets of patient samples collected in the early weeks of gestation. One set was urine samples, and the other was serum samples. In all cases, hCG and hCG-H were measured using automated chemiluminescence immunoassays. Concentrations of hCG and hCG-H were plotted on a scattergram, and levels in failing pregnancies were compared to those in continuing pregnancies.

RESULTS

Data indicated that a threshold level of hCG-H (13 microg/L) in both serum and urine samples defined the concentration below where pregnancies were likely to fail. This cut-off corresponded to 73% detection of failures at a 2.9% false positive rate using serum and 75% detection at a 15% false positive rate using urine. Using an hCG cut-off that corresponded to the same false positive rates, hCG detected only 42% of failures using serum and 43% of failures using urine.

CONCLUSIONS

Our data indicate that hCG-H provides a much more accurate single test than hCG for assessing pregnancy outcome. Compatible with the use of serum or urine samples, a single hCG-H test might provide simpler, faster, and more accurate results for predicting the progress of a pregnancy than standard hCG testing.

Sensitivity of Over-the-Counter Pregnancy Tests: Comparison of Utility and Marketing Messages

OBJECTIVE

To determine the sensitivity of seven over-the-counter pregnancy tests (OTC-PTs) using urine containing a mixture of human chorionic gonadotropin (hCG)-related molecules as found on the first day of missed menstrual period.

DESIGN

Blinded in vitro sensitivity analysis.

SETTING

Medical school laboratory.

PARTICIPANTS

None.

INTERVENTIONS

Urine was tested with OTC-PT devices at titers of 100, 50, 25, 12.5, 6.3, and 0 mIU/mL hCG immunoreactivity, and laboratory workers rated their confidence in the test result based on whether the test result was a clear, sharp, and unquestionable band in the test window.

MAIN OUTCOME MEASURES

Analytical sensitivity, defined as the urine concentration at which all OTC-PTs tested gave a positive result regardless of operator confidence score; clinical sensitivity of OTC-PTs, defined as the proportion of pregnancies likely to be detected on the first day of a missed period and calculated from the analytical sensitivity and a recently published regression curve for total urine hCG immunoreactivity in 25 urine samples from this period of gestation; percentage of tested devices showing a band in the test window at a specific hCG concentration measured devices positive; percentage faulty devices, defined as the proportion of tested devices failing to yield a band in the control window; and confidence score, determined from operator ratings for each device at each concentration of hCG.

RESULTS

First Response Early Result had an analytical sensitivity of 6.3 mIU/mL, which was estimated to detect greater than 95% of pregnancies on the day of missed period. The sensitivity of Clearblue Easy Earliest Results was 25 mIU/mL, which indicated detection of 80% of pregnancies. The sensitivity of the five other products was 100 mIU/mL or greater, indicating detection of 16% or less of pregnancies. Three of these last products included faulty devices.

CONCLUSION

Universal claims for OTC-PTs of more than 99% laboratory accuracy and use as early as the first day of missed period, while cleared for use by the U.S. Food and Drug Administration, are ambiguous and inappropriate for many products, according to these data. The majority of products tested were found to detect only a small percentage of pregnancies on the first day of a missed menstrual period. Until more data become available on the actual clinical sensitivity of these products, pharmacists should advise consumers to be cautious in interpreting test results.

Maternal Serum Invasive Trophoblast Antigen and First-Trimester Down Syndrome Screening

Background: In the United States, Down syndrome screening is still performed mainly in the second trimester, using 3 or 4 markers. Moving screening into the first trimester has the advantage of earlier diagnosis. Currently, first-trimester screening typically includes maternal serum pregnancy-associated plasma protein-A (PAPP-A), the free β-subunit of human chorionic gonadotropin (free β), and ultrasound measurement of nuchal translucency thickness (NT). The current report describes a case–control study of serum invasive trophoblast antigen (ITA) and its possible inclusion in first-trimester screening for Down syndrome.

Methods: As part of an earlier observational study, serum samples from 54 Down syndrome and 276 matched unaffected pregnancies were collected between 9 and 15 weeks of gestation. Samples had been aliquoted and stored at −20 °C for 8 years. ITA was measured and converted to weight-adjusted multiples of the median (MoM). The distributions of other first-trimester markers are from a single published study.

Results: Median ITA MoM in Down syndrome pregnancies increase as gestational age increases (2.02 MoM at 11 and 2.44 MoM at 13 completed weeks). At 75% detection, maternal age in combination with ITA and PAPP-A measurements have an 8.0% false-positive rate, slightly lower than the 8.8% found for the free β and PAPP-A combination; adding NT measurements reduces false positives for the 2 combinations to 2.0% and 1.8%, respectively.

Conclusion: Serum ITA appears to be a useful first-trimester Down syndrome marker that could replace free β measurements while maintaining performance.

Specific Measurement of O-Linked Core 2 Sugar-Containing Isoforms of Hyperglycosylated Human Chorionic Gonadotropin by Antibody B152

There have been a significant number of reports on the clinical utility of measurement of 'hyperglycosylated' isoforms of the pregnancy hormone, human chorionic gonadotropin (hCG). Although there are a variety of hCG isoforms which can be termed 'hyperglycosylated', the measurements were all made using a unique antibody designated B152. This antibody was raised using a choriocarcinoma-derived form of hCG, which was hyperglycosylated with N- and O-glycans and was also 100% 'nicked' hCG. Antibody B152 was recently mapped to a linear epitope around a single O-glycan on the beta-subunit of hCG at residue number 132. Thus, the antibody can only measure isoforms of hCG that possess a core 2 type of branched O-glycan on this portion of the hCG beta-subunit. Isoforms that are hyperglycosylated in the hCG alpha-subunit or only on the N-glycans of hCGbeta will not be recognized by antibody B152. Apparently, measurements of these core 2 hCG isoforms have important clinical application in early pregnancy during which they are the predominant isoform of hCG until the 6th week of gestation. The secretory pattern of these isoforms can be used to predict the health status of the pregnancy in fertility clinics. Moreover, the measurements of these core 2 hCG isoforms are more useful than standard hCG for the prediction of Down syndrome pregnancies. The core 2 isoforms are also of important use in cancer diagnosis and monitoring since their concentration appears to correlate with malignancy.

Biochemical screening for congenital defects

This article discusses biochemical screening for congenital defects. Biochemical screening remains the standard for estimating the risk of aneuploidy in pregnancy. The combination of first and second trimester markers promises to further improve diagnostic accuracy for anomaly detection.

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.

Maternal Serum Invasive Trophoblast Antigen (Hyperglycosylated hCG) as a Screening Marker for Down Syndrome during the Second Trimester

Background: Approximately two million pregnancies in the United States are screened for Down syndrome annually by use of second-trimester maternal serum markers. At present, a combination of four markers can identify 75% of affected pregnancies when 5% of screened women are classified as candidates for amniocentesis. Although not currently included in screening panels, invasive trophoblast antigen (ITA) is a promising screening marker in serum or urine in both the second and first trimesters. This study aims at better defining the screening performance of serum ITA in the second trimester.

Methods: In an earlier study, serum samples from an unbiased sampling of 45 Down syndrome (cases) and 238 unaffected (control) pregnancies between 14 and 20 weeks of gestation were collected from various centers in the United States. Samples were aliquoted and stored at −20 °C for 8 years. We measured ITA in these samples and determined the screening performance both univariately and in combination with other screening markers.

Results: The median ITA in Down syndrome pregnancies was &gt;3.00 multiples of the median, higher than that found for human chorionic gonadotropin (hCG) or free β-hCG. At a 5% false-positive rate, ITA univariately detected 38% and 40% of Down syndrome pregnancies, respectively, when assigned by date of last menstrual period or ultrasound date. Modeling yielded rates of 45% and 48%. ITA correlated strongly with hCG and free β-hCG. When substituted for either of these in a multiple marker panel, ITA performed comparably.

Conclusions: This study indicates that serum ITA is an effective marker for Down syndrome. It is highly correlated with both hCG and free β-hCG and could replace either of them in a multiple marker panel.

Hyperglycosylated hCG (invasive trophoblast antigen, ITA) a key antigen for early pregnancy detection

OBJECTIVES

Hyperglycosylated human chorionic gonadotrophin (hCG) is an hCG variant with extra-large O-linked oligosaccharides, produced by phenotypically invasive cytotrophoblast cells in choriocarcinoma and pregnancy. It is the principal form of hCG produced in the first weeks of gestation. We investigated the importance of hyperglycosylated hCG in pregnancy testing and its detection by current hCG tests.

DESIGN AND METHODS

We measured the concentration of hyperglycosylated hCG and total hCG in 512 pregnancies throughout gestation. We assessed and compared the abilities of 14 commonly used commercial laboratory hCG tests and 18 home pregnancy tests to detect regular and hyperglycosylated hCG.

RESULTS

Hyperglycosylated hCG is the principal source of hCG-related immunoreactivity in early pregnancy. In the week following missing menses, hyperglycosylated hCG measurements may be more sensitive than regular hCG measurements in detecting pregnancy. Of 14 commercial laboratory hCG tests, 3 appropriately detected hyperglycosylated hCG standard. Of 18 different home pregnancy products 11 poorly or very poorly detected this key antigen.

CONCLUSIONS

Hyperglycosylated hCG may be the key molecule in the detection of early pregnancy. However, the majority of tests poorly detected or failed to detect this key antigen. New pregnancy tests are needed that either solely detect hyperglycosylated hCG or equally detect regular hCG and hyperglycosylated hCG.

Between-Method Variation in Human Chorionic Gonadotropin Test Results

Background: Results on sera and calibrators vary 1.4- to 2.3-fold among commercial human chorionic gonadotropin (hCG) assays. The relative contributions of calibrators, standards, hCG charge isoforms, and major structural variants to this variation have not been quantified.

Methods: Purified hCG was separated by isoelectric focusing into four fractions with pI ranges of 3–4, 4–5, 5–6, and 6–7. These four fractions together with pure hCG, hyperglycosylated hCG, hCG β-subunit (hCGb), nicked hCG, and hCGb core fragment (hCGbcf) were tested in nine commonly used commercial serum assays for hCG. The compositions of pure hCG preparations, standards, and commercial hCG preparations were determined by immunoassay.

Results: The three pure hCG preparations and the four hCG charge isoforms each showed parallel responses in the nine commercial hCG assays. Although wide variations were found in the detection of hCG structural variants by the nine assays (range for hyperglycosylated hCG, 468-1544 IU/L; for hCGb, 3187-5535 IU/L; for nicked hCG, 2736-4240 IU/L; and for hCGbcf, &lt;2–130 IU/L), this did not correlate with the between-method variation observed in results for the three pure hCG preparations. Commercial preparations of hCG and calibrators showed great variation in their content of hCG structural variants (from 34% to 100% intact hCG).

Conclusions: Intermethod differences in hCG results were not explained by changes in responses attributable to hCG charge isoforms or to hCG structural variants, but wide variation was observed in concentrations of hCG structural variants in calibrators and in detection of these structural variants. Differences in assay specificity and in composition of the calibrators are the most likely sources of between-method variation.

Invasive Trophoblast Antigen (Hyperglycosylated Human Chorionic Gonadotropin) in Second-Trimester Maternal Urine as a Marker for Down Syndrome: Preliminary Results of an Observational Study on Fresh Samples

Background: Down syndrome screening is commonly performed in the US using maternal age and three or four second-trimester maternal serum markers that can identify up to 75% of affected pregnancies by offering diagnostic studies to 5% of women. Invasive trophoblast antigen [ITA; hyperglycosylated human chorionic gonadotropin (hCG)] is a promising marker that can be measured in urine or serum in the first or second trimester. We report preliminary results for urinary ITA in an ongoing observational study.

Methods: Women undergoing second-trimester amniocentesis for reasons not associated with biochemical testing provided consent and a urine (and possibly serum) sample that was tested within a few days. Demographic and pregnancy-related information was collected, along with karyotype. Screening performance was modeled for ITA alone and in combination with serum markers

Results: Twelve recruitment centers collected urine from 2055 women with singleton pregnancies between 15 and 20 weeks of gestation (2023 unaffected, 28 Down syndrome, and 4 pregnancies with other chromosome abnormalities). After correction for gestational age, urine concentration, and maternal race and weight, the ITA measurements were higher in women with a Down syndrome pregnancy (median ITA, 4.33 multiples of the median). At a 75% detection rate, the false-positive rate could be reduced by substituting ITA for hCG measurements (from 5.6% to 2.6% for the triple test) or by adding ITA measurements to existing combinations (from 3.3% to 2.0% for the quadruple test).

Conclusions: Our data provide preliminary confirmation of the potential usefulness of urinary ITA measurements in detecting Down syndrome in a setting that simulates routine usage.