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The human chorionic gonadotropin (hCG) test is done to measure the amount of the hormone hCG in blood or urine to see if a woman is pregnant. HCG may also be measured to see if cancer of the ovaries or testicles is present.
A qualitative HCG blood test checks if there is a hormone called human chorionic gonadotropin in your blood. HCG is a hormone produced in the body during pregnancy.
Other HCG tests include:
- HCG urine test
- Quantitative pregnancy test (checks the specific level of HCG in your blood)
Human chorionic gonadotropin is a hormone produced primarily by syncytiotrophoblastic cells of the placenta during pregnancy. The hormone stimulates the corpus luteum to produce progesterone to maintain the pregnancy. Smaller amounts of hCG are also produced in the pituitary gland, the liver, and the colon.[rx] As previously mentioned, certain malignancies can also produce either hCG or hCG-related hormones. Trophoblastic cancers (hydatidiform mole, choriocarcinoma, and germ cell tumors) are associated with high serum levels of hCG-related molecules.
Another Name
Human chorionic gonadotrophin – serum – qualitative; Pregnancy test – blood – qualitative; Serum HCG – qualitative; HCG in blood serum – qualitative
How the Test is Performed
A blood sample is needed. This is most often taken from a vein. The procedure is called venipuncture.
Urine Testing
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Urine should not be collected after the patient has been drinking a large amount of fluid, as a dilute specimen may result in a falsely negative test.[rx]
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Blood in the urine may cause a false positive test result.
Serum Testing
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Peripheral blood can be obtained for a serum hCG test.
How to Prepare for the Test
No special preparation is needed.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing.
Why the Test is Performed
Most often, this test is performed to determine if you are pregnant. HCG level in the blood may also be high in women with certain types of ovarian tumors or in men with testicular tumors.
Normal Results
The test result will be reported as negative or positive.
- The test is negative if you are not pregnant.
- The test is positive if you are pregnant.
What Abnormal Results Mean
If your blood HCG is positive and you DO NOT have a pregnancy properly implanted in the uterus, it may indicate:
- Ectopic pregnancy
- Miscarriage
- Testicular cancer (in men)
- Trophoblastic tumor
- Hydatidiform mole
- Ovarian cancer
Interfering Factors
There are multiple reasons why an hCG test (serum or urine) may have a false report. While uncommon, false-positive hCG tests can result in unnecessary medical care and/or irreversible surgical procedures. False negatives may be equally concerning and result in a delay in care or diagnostic evaluation. Potential causes of false results are listed and briefly discussed.
Serum False Positives (1/1000 to 1/10,000) [rx]
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Rheumatoid factors (can bind the antibodies in the assay as well)
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IgA deficiency[rx]
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Red blood cell or plasma transfusion of blood with hCG in it have been reported
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Exogenous hCG preparations for weight loss, assisted reproduction, doping[rx]
Serum False Negatives
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Early measurement after conception
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“Hook effect” can occur when hCG levels are about 500,000 mIU/mL.[rx] This is because there are so many hCG molecules that they saturate both the tracer and the antibodies separately, which doesn’t allow for the sandwiching of the tracer-hCG-antibody required for the measurement. This means that all of the complexes are washed away, giving a false-negative result. If the gestational trophoblastic disease is suspected, the lab should perform a dilution prior to testing.
Urine False Positives
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Blood or protein in the urine
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Human error in result interpretation
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Ectopic production of hCG
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Exogenous hCG
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Drugs (aspirin, carbamazepine, methadone, high urinary pH, and seminal fluid)[rx]
Urine False Negatives
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Early measurement after conception
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Dilute urine specimen[rx]
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“Hook effect” as discussed above
Risks
Risks of having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Blood accumulating under the skin (hematoma)
- Infection (a slight risk any time the skin is broken)
Considerations
False-positive tests may occur when certain hormones are increased, such as after menopause or when taking hormone supplements.
A pregnancy test is considered to be very accurate. When the test is negative but pregnancy is still suspected, the test should be repeated in 1 week.
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