A pregnancy test may let you know, one way or the other, if you are pregnant.
This test can also be completed to diagnose abnormal conditions that can raise HCG levels, or to watch the development of the pregnancy during the first 2 months (quantitative test only).
What is a pregnancy test?
A pregnancy test measures the amount of pregnancy hormone, human chorionic gonadotropin (HCG), circulating within a woman's body.1
Some sensitive pregnancy tests can be completed as early as 4 days before your period is due.
HCG hormone can be present in the blood and urine approximately 10-14 days following conception and peak between 8 and 11 weeks gestation.1,2
HCG is known as the pregnancy hormone, as it is produced by the cells that form the placenta and provides nourishment to the growing embryo.1,3
A negative HCG result is a level less than 5 mIU/ml, while a positive HCG for pregnancy is greater than or equal to 25 mIU/ml.2
How are pregnancy tests performed?
Pregnancy tests can be performed in one of two ways: urine or blood testing.
When testing at home or in an office setting using urine, the urine is placed on a chemical strip producing a result in approximately 1-2 minutes, although each brand of test may vary in the result times.1,3
These tests can be performed by collecting urine in a collection cup and either dipping the pregnancy test stick into the urine or placing the urine into a container using an eyedropper. Alternatively, a pregnancy stick can be placed into the urine stream.3
Each brand of testing has its own method of giving results so when looking for results it is important to read the package insert to determine how the results are given.
Some tests change in color, have line changes, or provide a symbol such as a plus, minus, etc. Other tests, such as digital ones, may provide you with a simple answer in the test window, for example the words "pregnant" or "not pregnant."3
When testing using blood, there are two forms of testing: a quantitative and qualitative HCG test.1-3
A quantitative blood test is used to measure the amount of HCG present in the blood, while the qualitative test simply tells you if HCG is present in the blood stream.1-3
While there are advantages to blood testing such as early pregnancy detection and the ability to measure HCG concentration, there are also disadvantages such as high cost, long result wait time and the need to have the test completed in a medical office.3
When should a pregnancy test be taken and what do the results mean?
When taking a home urine test, waiting until a period is missed is recommended. However, 14 days from possible conception would be the earliest possible time to take the test.3
Some tests have line changes, providing a symbol such as a plus or minus - the top test is negative and the one below is positive.
Some tests on the market can be taken earlier and depend on their individual sensitivity; read the package insert to determine the best and earliest time to take that particular test.3
The best time of day to take a urine pregnancy test is when you wake up in the morning.1
A positive home pregnancy test simply means that HCG is present in the urine, while a negative test can mean a variety of things.3
Negative tests can be truly negative or mean that the test was either taken too early to detect HCG or the test was taken improperly.3
How accurate are pregnancy tests?
When taken correctly, urine pregnancy tests offer approximately 97% accuracy. However, incorrect use of the test can result in a reading that is potentially inaccurate.3
If at first you receive a negative result but are exhibiting symptoms of pregnancy, it is recommended that you re-test in 1 week or speak with your health care provider about a blood test instead.3
References:
1.
NLM, Pregnancy test,
accessed 29 May 2015.
2.
American Pregnancy
Association, Human chorionic gonadotropin (HCG); the pregnancy hormone,
accessed 29 May 2015
3. American Pregnancy
Association, Understanding pregnancy tests:
urine & blood, accessed 29 May 2015
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