Serum Beta hCG

Specimen Required

3-5cc Clotted Blood or Serum

Fasting Required

Purpose of the Test

To confirm and monitor pregnancy or to diagnose trophoblastic disease or germ cell tumours

When this test is required

A qualitative urine hCG test can be done from the first day of a missed menstrual period if a woman wishes to confirm whether or not she is pregnant (some methods can detect hCG even earlier, at one week after conception). In certain patients, several quantitative blood hCG tests over several days may be requested to rule out an ectopic pregnancy or to monitor a woman after a miscarriage. A doctor will also request a quantitative hCG test if they suspect trophoblastic disease or the presence of a germ cell tumour.A blood test which includes hCG as part of the prenatal screening program for Downs syndrome is conducted during the 2nd trimester of pregnancy.

What the Test Detects

Human chorionic gonadotrophin (hCG) is a hormone produced in the placenta of a pregnant woman, , which starts to be produced around 6 days after fertilisation. A pregnancy test is a specific blood or urine test that can detect hCG and confirm or exclude pregnancy. During the early weeks of pregnancy, hCG is important in maintaining function of the corpus luteum (which is formed from the ruptured ovarian follicle following…Human chorionic gonadotrophin (hCG) is a hormone produced in the placenta of a pregnant woman, , which starts to be produced around 6 days after fertilisation. A pregnancy test is a specific blood or urine test that can detect hCG and confirm or exclude pregnancy. During the early weeks of pregnancy, hCG is important in maintaining function of the corpus luteum (which is formed from the ruptured ovarian follicle following ovulation). Production of hCG increases steadily during the first trimester of a normal pregnancy, peaking around the 10th week after the last menstrual cycle. Concentrations then fall slowly during the remainder of the pregnancy. hCG is no longer detectable within a few weeks after delivery. hCG is also produced by some germ cell tumours and increased levels are seen in trophoblastic disease. How is the sample collected for testing? hCG is most commonly measured in urine, for confirmation or exclusion of pregnancy. The preferred specimen is a random urine sample, which can be collected any time of day. Hormone levels are highest first thing in the morning so in early pregnancy it is usually best to test urine collected first thing in the morning to reduce the chance of false negative test results. hCG can also be measured in blood taken from a vein in the arm. See MoreSee Less

Preparation for the Test

None needed; however, do not drink large amounts of fluid before collecting a urine sample for a pregnancy test because overly dilute urine may result in a false negative test result.

Sample Requirements

Either a urine sample or a blood sample taken from a vein in the arm.

Additional Notes

Tests performed too early in the pregnancy, before there is a significant amount of hCG present in the blood or urine, may give false-negative results, while blood or protein in the urine may cause false-positive result. Urine hCG tests may give a false negative result in very dilute urine. Patients should not drink large amounts of fluid before collecting a urine sample for a pregnancy test.Certain drugs such as diuretics and promethazine (an antihistamine) may also cause false-negative urine results. Other drugs such as anti-convulsants, anti-Parkinson drugs, hypnotics, and tranquilisers may cause false-positive results.There are reports of false positive serum hCG results due to several different compounds (not drugs) that may interfere with the test. These include certain types of antibodies that may be present in some individuals and fragments of the hCG molecule. Generally, if results are questionable, they may be confirmed by testing with a different method.

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