- Main causes of false positive
- 1. Test done wrong
- 2. Chemical pregnancy
- 3. Use of some medications
- 4. Health problems
- How to avoid false positives
The pregnancy test can give a false positive result, however, this is a very rare situation that happens more frequently in pharmacy tests done at home, mainly due to errors when using it or because it is out of date.
Another common cause for this result is the so-called chemical pregnancy, in which the egg is fertilized, but is unable to implant properly in the uterus, eventually failing to develop. When this happens, the body begins to produce hormones to lead to pregnancy and, therefore, the first test is positive. However, as the pregnancy does not last, a new test some time later, can be negative.
In addition, women undergoing infertility treatment with hCG injections or who have tumors that are able to produce this hormone may also have a false positive result on the pregnancy test, either from a pharmacy or from a blood test.
Main causes of false positive
Changes in the result usually happen when the test is out of date and, therefore, it is very important to confirm the expiration date before using it. However, if it is correct, there are other causes such as:
1. Test done wrong
Before using the pharmacy pregnancy test it is important to read the manufacturer's instructions, especially regarding the time it is necessary to wait to read the result. This is because, some tests may show changes in the result after the recommended reading time.
In addition, before using the test it is also recommended to wash the intimate area with water, as some soaps or intimate creams may react with the test, leading to the appearance of a false positive or negative, for example.
Learn how to take the pharmacy pregnancy test and how to understand the result.
2. Chemical pregnancy
This type of pregnancy happens when there is fertilization of the egg, but the embryo has failed to fix itself in the uterus. In these cases, the body begins to produce the hormone hCG and, therefore, it can be detected in the urine or blood test, however, as the embryo was not in the uterus, it is eliminated and a spontaneous abortion with bleeding occurs, which can be mistaken with delayed menstruation.
3. Use of some medications
Some drugs used to treat infertility problems contain high amounts of hCG, the hormone that is evaluated in pregnancy tests and, therefore, can lead to a false positive shortly after treatment.
In addition, other more common medications like some anticonvulsants, diuretics or tranquilizers can also cause changes in the result. Thus, it is important to read the package insert or take the blood test at the hospital, informing the doctor about the medications used.
4. Health problems
Although it is more rare, the false positive can also arise in cases of disease, especially in cases of hormone-producing tumors, as in breast or ovarian cancer, for example.
How to avoid false positives
To avoid having a false positive result it is very important to follow all the instructions in the pharmacy test box and, after taking the test, be careful to:
- Repeat the test 3 to 5 days later; Do not re-confirm the test after the indicated time; Make an appointment with the gynecologist after 4 to 5 weeks.
However, the most reliable way to avoid changes in the result is to have the blood test with beta hCG evaluation, as in these cases there is less chance of changes in the result. In addition, before the test, the doctor makes an assessment to identify whether there are medications or other conditions that can cause a false positive. Learn more about the hCG beta exam.
