HCG in blood serum - quantitative

Definition

This is a blood test that measures the specific amount of HCG (human chorionic gonadotropin) -- a hormone produced during pregnancy.

How the test is performed

Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop 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.

Why the test is performed

Quantitative HCG measurements can allow precise prediction of the age of the fetus. It is also used when an abnormal condition that can elevate HCG level is suspected.

A pregnancy test is usually based on detection of HCG, which is secreted by the fertilized egg. HCG appears in the blood and urine of pregnant women as early as 10 days after conception.

Normal Values

Early in pregnancy, enough HCG hormone is needed to maintain the pregnancy. Later on, the placenta produces plenty of progesterone (another hormone) to keep the uterine lining thick and able to sustain the fetus through the remainder of the pregnancy. Therefore, HCG levels rise rapidly during the first trimester of pregnancy, and then drop off somewhat thereafter.

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

• fetal death
• incomplete miscarriage
• threatened spontaneous abortion
• ectopic pregnancy

What the risks are

Possible risks from any blood test include:

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations

Drugs that can decrease HCG measurements include diuretics and promethazine.

Drugs that can increase HCG measurements include anticonvulsants, antiparkinsonian drugs, phenothiazine, and promethazine.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Illustrations

Blood test

Page Content:

Serial beta HCG; Repeat quantitative beta HCG; Human chorionic gonadotrophin in blood serum - quantitative; Beta-HCG in blood serum - quantitative; Pregnancy test - serum - quantitative