Pregnancy test kits also called urine test kits for pregnancy are a convenient and easy-to-use method to test yourself for pregnancy at home if you have missed a period or exhibit early symptoms of pregnancy.
The pregnancy kit, which is available at most drug stores over the counter without a prescription, offers explicit instructions, which you can follow and do the test yourself at your home.
Additionally, it offers the advantage of convenience, and privacy, and is inexpensive. You can then see your doctor for advice, if the test is positive, or if the test is negative for more sensitive tests.
How do home pregnancy tests work?
The home pregnancy test is done by testing your urine. It works by detecting the presence of the Human Chronic Gonadotropin hormone, (hCG), which is a hormone produced in the body when a woman becomes pregnant.
HCG is produced by the embryo in the initial stages and later by the placenta. The concentration of hCG is low very early on after conception and its levels vary from woman to woman.
Some test kits are more sensitive and can detect hCG even in these early pregnancy stages. However, it is best to do a home pregnancy test about a day after the missed period. Some advise that it should be done a week after the missed period.
Doing the test before the missed period reduces the accuracy rate of the test result.
Best time to use a pregnancy test kit
There are different brands of home pregnancy kits available each with a different sensitivity.
Ideally, the test is most sensitive when done one day after the missed period. Opinions differ, but this is the best time to do the test.
Doing the test before the missed period reduces its accuracy because there may not be enough hCG in the urine that can be detected by the test strips.
However, improvements keep happening and newer kits with higher sensitivity levels keep coming.
For example, a test with a higher sensitivity, which can detect hCG levels in the urine of 10mIU/ml (milli-International Units per milliliter) will tell if you’re pregnant earlier than a test with a sensitivity of 25mIU/ml.
How to choose a pregnancy kit?
It is most important that you first read and understand the instructions given with the home pregnancy kit. They will vary slightly from kit to kit.
If possible, buy a kit that has an FDA license number on it. In many countries, these kits may not come under the FDA and therefore, such a number may not be present.
In such cases, you could identify a good kit by going in for one that is manufactured by a well-known reliable brand. The advantage is they may be more sensitive and will give you the result earlier. The disadvantage is they are more expensive. If expense is on your mind, you could use a generic kit if you don’t mind waiting for a few more days for the result.
Secondly, you have the option of going in for a regular kit with test strips or a digital home pregnancy test. Both are equally accurate except that the latter is more expensive.
Types of pregnancy home testing kits
There are two types of home pregnancy test kits.
Pregnancy test kit using strips
The most commonly used test kit consists of a testing strip, which you hold in your urine stream while urinating, or a dipstick, which you dip in the container in which you have collected your urine.
This has to be done immediately within 15 minutes of having passed urine. If there is a change of color in the marked area at the end of the strip, it means you are pregnant.
Different brands show different kinds of windows. Usually, most brands show two lines for a positive test and one line for a negative result.
The home pregnancy kit could also consist of a cup with a testing device. You put a few drops of urine with a dropper in the designated area of the device or immerse the device vertically in the cup of urine.
Pregnancy is indicated by a change in color in the designated area of the device due to interaction with hCG, which is present in a significant amount if the urine sample belongs to a pregnant woman.
Digital pregnancy kit
The second type is the digital pregnancy kit, which is used by placing the absorbent part of the strip in your urine midstream or vertically in a container containing your urine for 20 seconds. Lay the digital strip flat and read the results after 3 minutes. The small screen gives the result as “pregnant” or “not pregnant”.
Instructions for use
The instructions on the home pregnancy kit will tell you:
- what the kit is for
- when and how to perform the test
- how to collect and store the urine sample
- the procedure
- how to interpret the test results and
- what can interfere with the result
- The instructions may even ask you to avoid certain foods or medications or to limit your physical activity, which you should follow.
How to use the pregnancy test kit?
Read and understand the instructions on the home pregnancy kit literature or label and follow them precisely.
- You should use the first urine sample in the morning because it will be more concentrated. This will increase the accuracy of the test. Do not drink water before doing the test as it will dilute the urine.
- If that is not possible, use a urine sample, which has been passed at least four hours after the previously passed urine.
- Introduce the strip to the midstream urine sample, meaning let some urine pass before you introduce the strip to the urine stream.
- Lay the strip flat and wait for it to show the result.
- The pregnancy kit should be at room temperature. If it has been stored in a refrigerator, it should be brought out and kept so that it attains room temperature.
- Check the expiry date of the kit. An expired kit will not give correct results as the chemicals on the strip may have become inactive.
- Collect the urine in a clean and dry container or cup. There should be no traces of any previous substance or detergent in the container.
- You then introduce the strip to the collected sample as explained above.
- You should wait for 3 to 5 minutes (depending on the instructions) to see the result. Use a clock to be precise. Any impatience or delay in reading the results will give inaccurate readings.
- If the test is negative, do repeat the test one week later if you do not get a period. Or else, consult your doctor who may order the pregnancy blood test in a laboratory.
Accuracy of pregnancy test kit results
Home pregnancy tests can be quite accurate and reliable if used correctly.
A review has shown that home pregnancy tests are accurate to the extent of 97% when performed by technicians but the accuracy drops down to 75% when done by non-expert users.
This only shows that accuracy greatly depends on the test being properly performed. The instructions on the kit are fairly explicit and it is the failure to follow them properly, which drops the accuracy of the test and can give false negative or false-positive results.
You too can get high-accuracy results if you do the test correctly.
While reading the result on the kit strip, at times, you get a faint line and you wonder what to make of it. A faint line in the pregnancy test denotes a positive result, meaning you are pregnant. You could confirm it after a couple of days though.
False-negative and false-positive results: Causes
However, you may get a false negative or false-positive result with the pregnancy test kit. This can happen if you have not performed the test as per the instructions on the label of the kit.
You may get a false negative if you have performed the test too early in pregnancy.
You could get a false-positive result due to some medication you have been taking and which has interfered with the result.
If you get a positive pregnancy result and a subsequent test shows a negative result, you could possibly have had an early miscarriage.
It is advisable that you confirm the result of the home pregnancy test by following it up with a blood test for pregnancy by your doctor.
Medications that can give a false-positive result
According to the Pregnancy Tests Fact Sheet most over-the-counter and prescription medications such as antibiotics, painkillers, and birth control pills will not affect the results of a home pregnancy test.
Even hormone therapies that contain Clomid or Serophene (clomiphene citrate) will not affect the test result.
Narcotic drugs like ecstasy, cocaine, marijuana, heroin, and even alcohol will not affect a pregnancy test result.
However, if you are taking medicines that are used to treat infertility and contain hCG, the pregnancy hormone, it can cause a false-positive test result.
This is because they increase the levels of hCG in the urine. This can happen even if the test is performed within 7 to 14 days after you last took the drug. Examples include Humegon, Pregnyl, Profasi, Pergonal, and Novarel.