Beta HCG Total, Serum

Qualitative hCG testing detects the presence of hCG and is routinely used to screen for a pregnancy. This test may be performed by a laboratory, at a doctor's office, or at home using a home pregnancy test kit. Methods will vary slightly but for most, a test strip is dipped into a collected cup of urine or exposed to a woman's urine stream. A colored line (or other color change) appears within the time allotted per instructions, usually about 5 minutes. For accurate test results, it is important to carefully follow the test directions. (See the article on Home Testing: Avoiding Errors for more on this.) If the test is negative, it is often repeated several days later. Since hCG rises rapidly, an initial negative test can turn positive within this time period. Quantitative hCG testing, often called beta hCG (?
-hCG), measures the amount of hCG present in the blood. It may be used to confirm a pregnancy. It may also be used, along with a progesterone test, to help diagnose an ectopic pregnancy, to help diagnose and monitor a pregnancy that may be failing, and/or to monitor a woman after a miscarriage. hCG blood measurements may also be used, along with a few other tests, as part of screening for fetal abnormalities. For more information on this use, see First Trimester Down Syndrome Screen or Second Trimester Maternal Serum Screening. Occasionally, an hCG test is used to screen for pregnancy if a woman is to undergo a medical treatment, be placed on certain drugs, or have other testing, such as x-rays, that might harm the developing baby. This is usually done to help confirm that the woman is not pregnant. It has become standard practice at most institutions to screen all female patients for pregnancy using a urine or blood hCG test before a medical intervention, such as an operation, that could potentially harm a fetus.

How does the test that I do at home myself compare with the results of a test done in a lab?

Home pregnancy testing is very similar to qualitative urine hCG testing performed in the laboratory, but there are factors surrounding its use that are important to note.

Home tests come with very specific directions that must be followed explicitly. If you are using a home test, follow the directions extremely carefully (see Home Tests: Avoiding Errors). There can be variability in sensitivity to detecting the presence of hCG with different brands of home pregnancy kits.

Home tests are sometimes done too soon after the missed menstrual cycle to result in a positive test. It typically takes 10 days after a missed menstrual period before the presence of hCG can be detected by the urine test.

All urine hCG tests should be done on a first morning urine sample, if possible. Urine becomes more dilute after ingestion of liquids (coffee, juice, water, etc.) and urine hCG concentrations may become too low to register as positive.

Generally, when used correctly, the home test should produce the same result as the urine hCG test done by your health practitioner. Blood testing for hCG is more sensitive than urine hCG testing, so sometimes a blood test will indicate pregnancy when the urine test is negative.

When is a blood hCG test ordered instead of a urine hCG?

Since hCG is not normally detected in the urine of a non-pregnant woman, a urine hCG is enough to confirm a pregnancy. This can also be done with a qualitative blood hCG test. Sometimes, however, it is important to know how much hCG is present to evaluate a suspected ectopic pregnancy or to monitor a woman following a miscarriage. In these circumstances, a health practitioner will order a quantitative blood hCG test.

How many days after a miscarriage would it take for a urine pregnancy test to show a negative result?

Urine hCG decreases at about the same rate as serum hCG, which can take anywhere from 9 to 35 days, with a median of 19 days. However, the timeframe for when an hCG result will be negative is dependent on what the hCG level was at the time of the miscarriage. Frequently, miscarriages are monitored with quantitative blood hCG testing. If the levels of hCG do not fall to undetectable levels, some hCG-producing tissue may remain and have to be removed.

What is an ectopic pregnancy?

An ectopic pregnancy occurs when the fertilized egg (ovum) implants somewhere other than in the uterus. This is a serious condition needing immediate treatment. Women with ectopic pregnancies often have abdominal pain and uterine bleeding. Usually, abnormally low levels of hCG are produced in ectopic pregnancies with slower-than-normal rates of increase.