Whether a woman is trying to conceive or would rather not, one of the concerns foremost on her mind around the time of her expected period is whether she's pregnant. While determining pregnancy used to require a trip to the doctor's office and a complicated urine or blood test, these days it's possible to purchase easy-to-use, accurate home pregnancy tests, including e.p.t. at the drug store. Despite the general accuracy of the tests, however, false positives aren't unheard of.
Function
To understand how a pregnancy test, such as the popular brand e.p.t., can show a false positive, it's first important to understand how the tests work. Home pregnancy tests check for the hormone human chorionic gonadotropin, or hCG, in the urine. In theory, because hCG is produced only by the cells of a developing embryo, women who aren't pregnant can't have the hormone in their urine, and those who have the hormone in their urine must be pregnant. The e.p.t. brand test is among the more sensitive of pregnancy tests, according to the website Fertility Plus.
Use
For a home pregnancy test to be accurate, it's important to follow the instructions carefully. The e.p.t website notes that proper use of the test requires women to urinate on the absorbent test tip for five seconds, or dip the tip into a container of collected urine for twenty seconds. It takes two minutes for results to develop. A negative result is displayed as a horizontal line in the display window, while a positive result is displayed as a plus sign. One possible reason for a false positive result, notes the company, is inaccurate reading of the display window. They recommend that women familiarize themselves with the symbols for positive and negative results prior to testing to avoid reading errors. They also offer a digital test, in which the display reads "pregnant" or "not pregnant," to reduce user error.
Considerations
There are a few reasons that a pregnancy test might show a false positive result. The e.p.t. website notes that testing within eight weeks of a miscarriage or live birth can cause a false positive because women may still have hCG from the prior pregnancy in their bodies. Further, medications that contain hCG, found in some fertility drugs, cause false positive results. The site recommends that women who doubt the accuracy of the test result retest in a week, and verify the pregnancy with their doctor.
Prevention/Solution
Overall, false positive e.p.t. tests are much more rare than false negatives. The only possible reason for a positive test result under conditions in which the test is used correctly is hCG in the urine. Due to the rarity of false positives, therefore, it's quite difficult to prevent them; generally women who are at risk of a false positive are aware of the circumstances that create the risk, since they've recently been pregnant or have used fertility medication. The e.p.t. company does warn, however, that a test allowed to develop so long that it dries out may give what appears to be a positive result. This is not due to hCG in the urine, but is instead due to dye from the results window leaking as the test overdevelops. They recommend reading results no more than 10 minutes after beginning the test.
Warning
One further possibility for a positive pregnancy test is followed by menstruation. Sometimes, a newly implanted egg begins to produce hCG, giving a positive test, and then fails to complete implantation. This leads to a very early miscarriage; so early, in fact, that most women are not even aware that they were pregnant, with the exception of the positive test. Doctors Michael Roizen and Mehmet Oz, in their book, "You: Having A Baby", refer to such events as "chemical pregnancies." While they may be disconcerting to women who have tested positive for pregnancy, Roizen and Oz explain that these early miscarriages are quite common, unavoidable and perfectly normal.
References
- Fertility Plus: Pregnancy Tests
- e.p.t.: Factors that Affect Accuracy
- "You: Having A Baby"; Michael Roizen, M.D. and Mehmet Oz, M.D.; 2009
