Sep 11, 2008
Manufacturer's of today's home pregnancy tests claim that they are 99% effective when properly
used. The only more accurate tests are blood tests administered by physicians. But when
and how to use them, and which are the most accurate are questions that still remain. Are they all
the same? What if the test is negative, but "I just have that feeling. . ."?
Pregnancy test work by detecting Beta-hCG (human chorionic gonadotropin), a hormone produced
by the placenta in a pregnant woman's uterus. The hormone is then released into the blood stream and ultimately excreted in the urine. HCG usually becomes detectable in the urine about 10 days after conception, or about 4-5 days before the missed menstrual period. Because it can be difficult to know exactly when conception occurred, or
when exactly the period is supposed to start, most experts recommend waiting 5-10 days after the period is late
to ensure that the test is accurate.
Most pregnancy tests on the market will show a positive result by 7-10 days after the missed menstrual period. Often though, it may be desirable to have the result earlier. Some of the home tests are accurate enough to detect the HCG as soon as it is present, even at very low levels. Two studies have confirmed claims of the manufacturers of FIRST RESPONSE Early Result Test to detect a pregnancy five days before the missed period. Clear Blue Easy claims to be accurate within 4 days before the missed period. If you want to know as quickly as possible,these two brands are probably the best tests to use, but you will need to be willing to pay a little extra for that privilege!
It is certainly possible to have a false negative (test result is negative when the woman actually is pregnant).
A study done in 2004 evaluated 18 different home pregnancy tests and found that they missed up to 85% of pregnancies when testing was done on the first day of the missed period. Almost all of them had become positive by
one week after the missed period. So if your first test is negative wait a week and test again.
How to improve the accuracy of your tests:
*Use urine collected first thing in the morning--it is more concentrated. You can collect the urine and save it in a labeled container in the refrigerator if you need to run to the store for the test kit.
*Don't drink too much fluid before testing. This will dilute the urine.
*If you are testing later in the day, make sure it has been at least four hours since you last emptied your
*Check the expiration date on your test.
*Follow the directions exactly as specified in the package insert.
*Read the instructions to make sure you are not taking any medications that will alter the test results
Other things to note: A pregnancy problem (impending miscarriage, tubal pregnancy, etc.) can cause a false negative result. Rarely infertility medications can cause a false positive result(test result is positive when the woman is not pregnant). Finally, HCG causes some of the typical early pregnancy symptoms such as breast tenderness and nausea, so eventually, your own body will be likely to alert you.
The best way to double check if you suspect your test is not accurate, or if you simply need peace of mind, is to visit your doctor or local clinic. Many doctor's offices or clinics offer free pregnancy tests--so inquire before going in.
If you would like more information go to: http://www.womenshealth.gov/faq/pregtest.htm