HCG blood test - quantitative
Definition
A quantitative human chorionic gonadotropin (HCG) test measures the specific level of HCG in the blood. HCG is a hormone produced during pregnancy.
See also:
Alternative Names
Serial beta HCG; Repeat quantitative beta HCG; Human chorionic gonadotrophin blood test - quantitative; Beta-HCG blood test - quantitative; Pregnancy test - blood - quantitative
Why the Test is Performed
HCG appears in the blood and urine of pregnant women as early as 10 days after conception. Quantitative HCG measurements can help to diagnose abnormal preqnancies, such as ectopic pregnancies, molar pregnancies, and those that will miscarry. It is also used as part of a screening test for Down Syndrome.
This test is also done to diagnose abnormal conditions unrelated to pregnancy that can raise HCG levels.
How the Test is Performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
How to Prepare for the Test
No special preparation is necessary.
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Risks
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Considerations
Drugs that can decrease HCG measurements include diuretics and promethazine.
Drugs that can increase HCG measurements include anticonvulsants, anti-parkinsonian drugs, phenothiazine, and promethazine.
Normal Results
HCG levels rise rapidly during the first trimester of pregnancy and then slightly decline.
What Abnormal Results Mean
Higher-than-normal levels may indicate:
- Choriocarcinoma of the uterus
- Hydatidiform mole of the uterus
- Normal pregnancy
- More than one fetus -- for example, twins or triplets
- Ovarian cancer
- Testicular cancer (in men)
Reviewed By: Linda Vorvick, MD, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; and Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Redmond, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
