Beta-hCG Test - Human Chorionic Gonadotropin, Quantitative

Beta-hCG is produced by certain tumors or tumor cells, especially those that develop from an egg or sperm, and as such is a tumor marker for the ovaries and testicles. Human chorionic gonadotropin (hCG) is a hormone that is also produced by an embryo after implantation.

This quantitative blood test measures levels of Beta-HCG, which is produced by certain tumors, especially those that develop from an egg or sperm. 

Overview

Human chorionic gonadotropin (hCG) is composed of glycopeptide α- and β-subunits. The β-subunit is unique to hCG, whereas the α-subunit is essentially identical to that of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid stimulating hormone (TSH). Current assays detect both subunits, avoiding false positives of older tests caused by overlapping α-subunits. It is now realized that there are several molecular variant forms of hCG. The clinical application of these newly recognized forms is evolving but confusion exists due in part to inconsistent terminology and a lack of laboratory standardization for detecting and reporting the various forms.

Detection and monitoring of pregnancy is the only FDA approval for the majority of clinical hCG assays. These tests detect the β-subunit of regular hCG, determined as either intact or total hCG (free β-hCG plus intact). More sophisticated testing can now identify variant forms in urine or serum, two of which are clinically relevant: hyperglycosylated-hCG (hCG-H) and a hyperglycosylated free β-subunit (β-hCG-H). These three clinically significant forms (regular hCG, hCG-H, and β-hCG-H) are present in differing amounts in the course of normal pregnancy as well as diseased states such as abnormal pregnancies, gestational trophoblastic disease (GTD), aneuploidy, and germ cell tumors (Cole, 2009). Commonly used assays that detect intact or total hCG may be better suited for simply detecting pregnancy as opposed to more sophisticated assays (eg, hCG-H) intended for the purpose of evaluating suspected pathology.

Qualitative tests detect the presence of intact or total hCG as opposed to this test (a quantitative test) which detect the level. Sensitivity is determined by the detection limits of a given assay, and the amount of hCG produced (dependent on timing of implantation, usually about 8 days after ovulation). Less commonly realized is that sensitivity also depends on which clinically relevant forms of hCG are being detected. As already stated, hCG assays vary considerably and include over-the-counter qualitative tests, point-of-care qualitative serum and urine tests, and laboratory quantitative serum assays (Cole, 2009), the last being most useful for evaluating early and abnormal pregnancies (ectopic/miscarriage), GTD, and certain malignancies.

Uses for This Test

• Detect and monitor pregnancy
  • Evaluation of women with abdominal/pelvic pain, abnormal menstrual bleeding
  • Screen women at risk for pregnancy prior to radiologic imaging, surgery, or use of some medications
• In a workup of suspected ectopic pregnancy, serial hCG testing is used (usually in combination with transvaginal ultrasound).
• Fetal aneuploidy screening, in combination with other maternal serum analytes and ultrasound as a part of first trimester, second trimester, or combined first and trimester screening for trisomy 21 and trisomy 18.
• Management of gestational trophoblastic disease (GTD) and neoplasia. Such tumors include complete and partial hydatiform mole, invasive mole, gestational choriocarcinoma, and placental trophoblastic tumors.
• Evaluation and treatment of nonpregnancy-related conditions, such as a postpartum enlarged uterus, enlarged testicle, or mediastinal mass, which may be due to germ cell tumors.