Lab Test: hCg, Quantitative (Serum) Level
- Diagnose pregnancy
- Monitor high-risk pregnancies
- Tumor marker for hCG-producing cancers
- The placental trophoblast secretes human chorionic-gonadotropin (hCG) when the ovum is fertilized and is used to for detection by all pregnancy tests. hCG is made up of alpha and beta subunits. The beta subunit is specific for hCG. Immunologic tests are performed by using commercially prepared antibodies against the hCG and its subunits (particularly the beta subunit). Most of these laboratory methods use sandwich type immunoassay.
- hCG can appear in the blood and urine of pregnant women as early as 10 days after conception. In the first few weeks of pregnancy, hCG rises markedly, and serum levels are higher than urine levels. Results can be confirmed with a repeat test in 72 hours. Values in pregnancy should double every 2-3 days for the first 6 weeks. When an embryo is first large enough to be visible on transvaginal ultrasound, the patient generally will have hCG concentrations between 1000 and 2000 IU/L. If the hCG value is high and gestational contents are not visible in the uterus, ectopic pregnancy is suggested.
- In conditions outside of pregnancy, hCG may be secreted by seminomatous and non-seminomatous testicular tumors, ovarian germ cell tumors, gestational trophoblastic disease (e.g., hydatidiform mole), and benign or malignant nontesticular teratomas.
- Increased levels may indicate:
- Pregnancy, ectopic pregnancy, hydatidiform mole of uterus, choriocarcinoma of uterus, germ cell (choriocarcinoma, teratomas, embryonal cell) tumors of tests or ovaries, other tumors (poorly differentiated tumors, such as hepatoma and lymphoma)
- Decreased levels may indicate:
- Threatened abortion, incomplete abortion, or a dead fetus
- Tests performed too early in the pregnancy, before there is significant hCG level, may give false-negative results.
- Hemolysis of blood may interfere with test results.
- Drugs that may cause false-positive results include: anticonvulsants, antiparkinsonian drugs, hypnotics, and tranquilizers (especially promazine and its derivatives).
- Collect a venous blood sample for serum testing.
- Apply pressure or a pressure dressing to the venipuncture site and assess the site for bleeding.
- Explain the procedure to the patient.
- Emphasize to the patient the importance of antepartal health care.
Indications & Uses
What To Tell Patient Before & After
MESH Terms & Keywords