b-hCG is known as Beta Human Chorionic Gonadotropin. The b-hCG test is also known as the pregnancy test or Total hCG test. b-hCG test measures the levels of b-hCG in the blood. b-hCG is normally produced by the cells of the developing placenta, during pregnancy. However, high levels of b-hCG are also seen in certain tumors (cancer).
Why is b-hCG done?
To confirm pregnancy
To diagnose pregnancy in the location other than the normal (Ectopic pregnancy)
For first trimester screening of genetic diseases like Down's syndrome and Trisomy 18
To diagnose the presence of Gestational Trophoblastic Disease (GTD)
To diagnose any suspected tumors like Teratomas, Testicular Tumours, Ovarian Germ Cell Tumours.
What does b-hCG Measure?
b-hCG test measures the levels of b-hCG in blood. b-hCG is a hormone which is normally produced by the cells in the developing placenta, during pregnancy. b-hCG levels increase during the initial period of the pregnancy. The role of b-hCG in early pregnancy is to maintain the corpus luteum (the hormone-secreting structure that develops in an ovary). During the first three weeks, production of b-hCG increases reaching to peak levels at 10th week (from the last menstrual cycle). After that, the levels of b-hCG start falling to negligible levels within a few weeks after delivery.
In men and women, b-hCG is normally found in small amounts. b-hCG is composed of two big molecules known as alpha and beta subunit. The structure of the alpha subunit is similar to the structure of Follicle-stimulating hormone and Luteinizing hormone. The beta subunit is different and is found only in b-hCG. That is why b-hCG test is done to decrease the risk of cross-reaction.
How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle is used to withdraw blood from a blood vessel in your arm. The healthcare provider will tie an elastic band around your arm to make the blood vessels swell with blood. This makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You will feel a tiny pinprick during the procedure. Blood sample once collected will then be sent to the laboratory.
Is there any risk associated with this test?
There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in very rare cases, a patient may experience increased bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.
Should beta hCG levels be checked in routine?
This test is not done routinely. This test is advised in case of bleeding, severe cramps or if the patient has any history of miscarriage.
Is the beta hCG test only used for pregnancy?
No, b-hCG is considered to be a tumor marker as it is also secreted by some of the tumors which show high levels of b-hCG for e.g. the cancer of the uterus, ovarian cancer, lung cancer, and breast cancer. There are also some non-cancerous conditions which show increased levels of b-hCG such as Cirrhosis and inflammatory bowel diseases.
Is the beta hCG test always 100 % accurate?
No, it can give false positive and false negative results for pregnancy. In case of any doubt, the test is redone to ensure the pregnancy is there or not. Secondly, patients on medicines containing b-hCG can disrupt the levels of b-hCG in the test such as fertility drugs.
When are the results False-negative in beta hCG test?
False-negative results mean that the test result is indicating negative wrongly. Generally, false-negative b-hCG results mean that the patient is not pregnant. But, if the tests have been performed very early during the pregnancy, the results would be negative. The b-hCG levels change quickly with the duration of pregnancy.
When are the results False-positive in beta hCG test?
False-positive results mean that the test result is indicating positive wrongly. Patients on certain medications containing b-hCG can show a false-positive test. People who smoke marijuana also show a false-positive test.
Are beta hCG levels positive in ectopic pregnancy as well?
Yes, b-hCG levels are positive in an ectopic pregnancy (pregnancy other than its normal location) but the levels increase slowly as compared to normal pregnancy.
Can beta hCG levels be detected positive in neonates?
Yes, b-hCG levels can be detected positive in neonates because b-hCG is produced by the cells in the placenta which passes the placental barrier and thus found in neonates.
Can beta hCG levels be found positive in men also?
Yes, b-hCG levels can be found positive in men in case of testicular cancer.
Are there any other tests required with the beta hCG test for confirmation of pregnancy?
If your doctor confirms pregnancy, he will advise you PAPP-A test for prenatal screening in the first trimester or Dual marker test can be advised.
Interpreting b-hCG results
Low b-hCG levels are seen in the following conditions:
Error in calculation of pregnancy date
The blighted ovum (Pregnancy without embryo)
Ectopic pregnancy (Pregnancy other than normal location or outside of the uterus)
High b-hCG levels are seen in the following conditions:
Error in calculation of pregnancy date
Molar pregnancy (an abnormal pregnancy where the baby does not develop)