HCG - quantitative

Alternative names
Serial beta HCG; Repeat quantitative beta HCG; Quantitative serum beta-HCG; Human chorionic gonadotrophin - quantitative serum; Beta-HCG - quantitative serum

Definition
This is a blood test that measures the specific amount of HCG (human chorionic gonadotropin).

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 fill 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.

HCG maintains progesterone production by the corpus luteum in the early part of pregnancy. By the time HCG levels drop at the beginning of the second trimester, the placenta can make sufficient progesterone to maintain the uterine lining (endometrium). However, HCG may also be elevated in abnormal circumstances in men as well as women.

Normal Values
Beta-HCG levels vary with gestational age during pregnancy.

What abnormal results mean
Higher-than-normal levels may indicate:

     
  • choriocarcinoma of the uterus  
  • hydatidiform mole of the uterus  
  • normal pregnancy  
  • ovarian cancer  
  • testicular cancer

Lower-than-normal levels may indicate:

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

What the risks are

     
  • 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.

Johns Hopkins patient information

Last revised: December 4, 2012
by Harutyun Medina, M.D.

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