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Human Chorionic Gonadotropin Testing
|Synonyms||HCG; Beta-HCG; b-HCG; gonadotropin tests; choriogonadotropin; pregnancy testing; UCG|
|Additional information||Assays for ß-HCG are employed to assess the possibility of pregnancy, to aid in detecting the presence of a hormone-producing tumor such as choriocarcinoma, or as part of a multifactorial analysis to estimate the risk of a pregnant woman carrying a fetus with Down syndrome (see Alpha-Fetoprotein). The most specific assays utilize monoclonal antibodies to the ß-subunit of HCG to minimize cross-reactivity with other gonadotropins, particularly LH.
When using HCG levels to monitor tumor activity, it is important to ensure that the reagents employed are capable of detecting not only intact HCG, but also free ß-chains (intact or fragmented), the latter of which can be the predominant product of some tumors.
HCG for Down syndrome see Alpha-Fetoprotein.
HCG for Pregnancy, Urine: Suitable for routine and particularly stat pregnancy testing at the time of the first missed menstrual period. Results are reported as positive/negative. This is the only pregnancy test routinely covered by MediCal in the absence of a demonstrated ectopic pregnancy.
HCG for Pregnancy, Serum: Suitable for pregnancy testing at or slightly before the time of the first missed menstrual period. During the first six weeks of normal pregnancy, serum levels of HCG can be expected to double every 1.5-2.5 days. To follow up results in the inconclusive range (5-20 IU/L) it may be helpful to repeat the test after 3-5 days. HCG levels vary widely between individuals, and "normal" ranges during different stages of gestation are difficult to define. However, values between 20-200 IU/L typically reflect early pregnancy. Levels in an ectopic pregnancy are often lower than in normal intrauterine pregnancy. HCG levels can also be employed to monitor the physiologic status of an implanted fertilized ovum, falling levels, e.g., suggesting fetal loss.
Note: Serum HCG should be confirmed by urine hCG testing. An elevated serum hCG with a negative urine hCG suggests a false posivive result in the serum assay.
HCG for Tumor, Serum This test is useful both for monitoring the treatment and detecting the recurrence of HCG-secreting tumors. This test was developed by the Clinical Laboratories at the Medical Center at UC San Francisco. It has not been cleared or approved by the U.S. Food and Drug Administration.
|Last Updated||4/21/2008 9:43:03 AM|