Human chorionic gonadotropin (hCG) is the basis for all pregnancy tests.1 It is mainly produced by the syncytiotrophoblast cells of the placenta during pregnancy and can also be seen in gestational trophoblastic diseases (choriocarcinoma, hydatidiform mole) and testicular germ cell malignancies.1,2,3,7 It has been shown that the hCG produced through the majority of normal pregnancy is a smaller molecule than the hCG produced in choriocarcinomas and malignancies, due to four double sized O-linked oligosaccharide side chains of the molecule.8 Lesser differences are also found on the N-linked oligosaccharides.8 This larger molecule is named choriocarcinoma hCG, or hyperglycosylated hCG (hCG-H).
hCG-H is a cytokine-like molecule3 produced by stem cytotrophoblast cells, which are invasive cells that are active during implantation of the blastocyst in pregnancy.1,2,3 A monoclonal antibody (antibody B152) has been generated that has 0% cross-reactivity with regular hCG.9 An automated chemiluminescence assay is now marketed by Nichols Institute Diagnostics using B152 and an anti-β tracer antibody.3 This allows us to determine the immunoreactivity of hCG-H in urine and serum samples. Many studies have now shown hCG-H to be the most predominant form of hCG in early pregnancy. 1,3,4,5,6
Since there is such as high proportion of hCG-H in the first weeks of pregnancy, it is being studied to determine its significance as a marker of early pregnancy. This paper will review studies determining the effectiveness of using hCG-H to monitor pregnancy outcome, as well as studies researching the sensitivities of commercial pregnancy tests to hCG-H.
Scope of literature review
Research for this literature review was done using Web of Science. Articles were found by mapping references to and from A Single Serum Test for Measuring Early Pregnancy Outcome with High Predictive Value by L.A. Cole et al.4 Most research available on hCG-H was done by researchers out of the University of New Mexico. Therefore, searches were done by author name to view the full body of work published. Supplemental searches to gain background knowledge about pregnancy, pregnancy testing, and pregnancy failure were done using Google.
hCG-H AS A MARKER FOR PREGNANCY TESTING
Laurence A Cole et al. have done two separate studies, one in 2001 another in2003, assessing home pregnancy tests and their detection of hCG-H.1,6 Both studies showed that hCG-H is responsible for the majority of immunoreactivity in the 4th completed week of gestation at the time of missed menses.1,6 This indicates hCG-H is a more sensitive marker of pregnancy than regular hCG. Tests which measure hCG-H equally to, or better than, regular hCG may be optimal pregnancy tests.
Early pregnancy loss (pregnancies that briefly implant then fail within the first six weeks) is characterized by an increase in hCG that usually returns to near-normal levels by the time of missed menses.1 This can...