Are Home Pregnancy Tests Accurate?
The first thing many women do after missing a period is purchase a home pregnancy test. Available without a prescription, home pregnancy tests can be purchased at most drugstores, supermarkets and grocery stores. These tests allow women to test for pregnancy as soon as they begin to notice pregnancy symptoms rather than wait for a doctor’s appointment. Early pregnancy detection gives women the opportunity to begin prenatal care as early as possible. A home pregnancy test is not a foolproof method of detecting a pregnancy because to is susceptible to errors due to user error. Knowing what is involved with home pregnancy testing prior to taking the test can help ensure that the test is performed properly, significantly increasing the odds of an accurate result.
When Should I Take A Home Pregnancy Test?
Knowing when to take a home pregnancy test all depends on the test manufacturer. While just about all home pregnancy tests will detect a pregnancy shortly after a missed period, there are some manufacturers who have developed tests that can confirm a pregnancy as early as 7 days prior to a missed period. These early detection tests, however, have a higher incidence of false negatives. This is because some pregnant women will not have enough pregnancy hormones circulating in their blood this early. For this reason, it is best to take a pregnancy test at least one week after a missed period. Women who take a test earlier than that and get a negative result should retest a few days later if their period does not begin.
What Kind Of Home Tests Are There?
There are several options for home pregnancy tests. The majority of home pregnancy tests require the woman to insert the tip of a dipstick into their urine, midstream.
- The stick is held in place for 5 seconds to allow the urine to completely saturate the test area.
- Some tests provide a small collection container for the woman to collect her urine in.
- The dipstick is then inserted into the container and held there for up to 10 seconds.
- If a test kit does not include a collection cup, any clean cup or other small container can be used.
- The dipstick is then placed on a flat surface and left to develop for 5 minutes. After 5 minutes the test can be read.
- Older tests used to include a small syringe dropper that was used to suck up the urine out of the container. A few drops are then squeezed out onto a testing plate. Though most manufacturers replaced these types of tests with the dipstick, there are a few who still offer this method.
There are a few different ways to reveal the test result. This varies among manufacturers. Some brands offer multiple testing kits, each with a different method of reading results.
- Dipsticks contain 2 windows. The first window is the control window. A thin line, usually blue, appears in the control window to confirm that the test worked.
- If a line does not appear in the control window, the test is not valid. This can happen as a result of not enough urine, too much urine, improper technique or a defective test.
- Regardless of the reason, a new test will need to be taken. Fortunately, most test kits contain multiple tests.
If the line is present in the control window, the test has worked. The second window is the test window.
- This is where the test results are read. If a pregnancy test is positive, the second window will contain an identifying mark.
- This mark depends on the brand of tests used. Some will have one line just like the one in the control window.
- Others will show one line in the test window if the test is negative and two lines if it is positive.
- Other possible symbols are a plus or minus sign, a smiley face, a change in color or the words ‘pregnant’ or ‘not pregnant’.
- Read the instructions that come with the kit carefully to be sure you are looking for the correct symbol and interpreting the results properly.
- The instructions can vary among different brands, so always be sure to read the directions carefully prior to testing.
- Almost all home pregnancy kits include a 24 hour toll-free information line to answer questions about the kit.
How Do They Work?
Home pregnancy tests contain sensitive antibodies that detect tiny amounts of the pregnancy hormone HCG in urine. After the egg is fertilized it will implant into the uterus. The fertilized egg, or embryo, will then begin to release HCG into the body. HCG is needed for the pregnancy to grow and thrive. This hormone is secreted approximately one week before a missed period. The amount of HCG present in early pregnancy varies among women. While some women will have enough HCG to detect a pregnancy prior to a missed period, others will not have enough until two weeks later.
How Accurate Are Home Pregnancy Tests?
All pregnancy tests are regulated by the Food and Drug Administration (FDA), which means that all pregnancy test manufacturers have to live up to the same standards. For this reason, all brands are relatively equal in accurately detecting pregnancy. Most tests have an accuracy rate of 99 percent in detecting pregnancy when used at least one day after a missed period. Home pregnancy tests administered after a missed period are usually very reliable as long as testing is done correctly and according to instructions.
False positives are relatively rare, but can sometimes occur. Women who are taking fertility medications that contain HCG can have a false positive result. False positives can also occur in women who have recently been pregnant, women who have ovarian cysts and women going through menopause.Still relatively uncommon, false negatives occur much more often than false positives.
What Could Cause a False Negative?
The main reason for a false negative is testing too early. The development of tests that claim to detect HCG up to a week before a missed period lead many women to test earlier. Although some women will have a positive test at this early stage, many will not, even if they are in fact pregnant. Testing a few days after a missed period decreases the chance of a false positive by up to 70 percent.
Another factor in false negatives is improper timing. If the test is checked for a result before the urine has had a chance to interact with the HCG-detecting antibodies in the test, the symbol that identifies pregnancy may not have time to show up. Always follow the package instructions and wait the designated amount of time before reading results. All test results should be considered invalid after one hour.
First morning urine is recommended when testing for pregnancy. This is because the urine is more concentrated and has not been diluted from drinking liquids. Testing midday or in the evening can lead to a false negative is the urine is not concentrated enough.
What Happens Next?
- If your home pregnancy test is negative but you still do not get your period, retest in a few days. If after retesting your period does not start within a week, schedule an appointment with your physician to determine the underlying cause.
- If your test is positive, you will still need to schedule a doctor’s appointment. Your doctor will likely repeat the test in the office and order a blood test to confirm the pregnancy. Additional tests such as a pelvic exam and ultrasound may be ordered.