Human Chorionic Gonadotropin (hCG)
hCG testing detects the presence of hCG and is generally used to screen for pregnancy. The test will check for hCG levels in the blood or urine. hCG is produced by the placenta during pregnancy.
Quantitative hCG testing, often called beta hCG (ß-hCG), measures the amount of hCG present in the blood. It may be used to confirm a pregnancy. The test may also be used, along with a progesterone test, to help diagnose an ectopic pregnancy, to help diagnose and monitor a pregnancy, and/or to monitor a woman after a miscarriage.
Qualitative hCG testing measures whether the hCG hormone is present at all.
hCG blood measurements may also be used, along with other tests, as part of screening for fetal abnormalities, such as Down syndrome.
Occasionally, an hCG test is used to screen for pregnancy if a woman is to undergo a medical treatment, be placed on certain drugs, or have other testing, such as x-rays, that might harm the developing baby. This is usually done to help confirm that the woman is not pregnant.
Blood or protein in the urine may cause false-positive pregnancy results. Urine hCG tests may give a false-negative result if the urine is too diluted or if testing is done too soon in the pregnancy.
Certain drugs such as diuretics and promethazine (an antihistamine) may cause false-negative urine results. Other drugs such as anti-convulsants, anti-parkinson drugs, and tranquilizers may cause false-positive results. The presence of protein in the urine (proteinuria), blood in the urine (hematuria), or excess pituitary gonadotropin may also cause a false positive.
Consult with your doctor to guide you on the details of the hCG test for your specific situation.