Pregnancy tests are one of the most accurate methods to determine pregnancy at home. In addition, they are very simple to use, can be done very quickly and are relatively inexpensive. However, a lot of women are concerned about the issue of pregnancy test accuracy. Can a woman trust a pregnancy test result?
Briefly About Pregnancy Tests
There are various tests to determine pregnancy. The simplest and cheapest ones are test strips. They are very popular among women, but they are less accurate compared to more expensive and high-quality midstream sticks. In general, the accuracy of modern tests is very high – more than 99%. One percent manufacturers always leave for the right to make a mistake. There are a number of reasons why tests can show a false result. But in recent years, gynecologists have become increasingly skeptical about the use of home tests. Today, doctors determine their accuracy as not exceeding 97%, and often much lower. Nevertheless, if you do everything correctly and take into account the factors influencing the result, the test can show a fairly accurate result.
Pregnancy Tests: Mechanism of Action
The action of any home test designed for determining early pregnancy is based on the detection of human chorionic gonadotropin (hCG). This is a specific pregnancy hormone. This hormone begins to be produced one day after the implantation (attachment) of the fertilized egg to the wall of the uterus. It approximately corresponds to one week after conception.
As you already know, the maturation of the egg and its release from the ovarian follicle most often occurs in the middle of the menstrual cycle. That is, on the 14th day (counted from the first day of the last menstruation) with a menstrual cycle of 28 days. Fertilization of this egg can occur within 3-4 days. According to some authors this period is more significant – from 12 to 24 hours to 7 days. Then, if fertilization of the ovulated egg occurs, it moves along the fallopian tube into the uterine cavity for 5-6 days. It stays in the uterus cavity in a free (not attached) state for some time.
After 6-7 days of the intrauterine period, the fertilized egg attaches to the inner layer of the uterus (endometrium). After that it is implanted into the uterine wall and begins to develop. The development of pregnancy from the moment of implantation is accompanied by the production of hCG. If you combine all the terms of embryo development from ovulation to implantation, it becomes evident that hCG in a small amount enters the blood of a pregnant woman already a few days before the expected menstruation. In urine this hormone gets a bit later.
HCG in the Blood and Urine
In medical laboratories, HCG is measured in the blood, revealing pregnancy sometimes several days before the expected menstruation, but this does not apply to home tests. Home tests give a reliable result in the presence of at least one day of delay in menstruation. And if we take into account that the organism of each woman is individual (early or late ovulation is possible), the characteristics of sperm in individual men are also not identical, it can be argued that the time of reliable determination of pregnancy in the early stages, both at home and in the laboratory, can significantly vary.
Pregnancy Test Accuracy: Why Can a Test Show a False Result?
Why do some tests give an accurate result in the first days of pregnancy, and others do not work? The reasons can be different. For example, a test was conducted incorrectly or too early, deteriorated due to the expiry date or improper storage.
A pregnancy test may show a false result if a woman takes diuretics, has a kidney or cardiovascular disease that affects the release of the hormone in the urine. A test will also not determine ectopic pregnancy. Therefore, consult a doctor for a more serious examination. Do not wait for menstruation, make blood or urine tests. They are more reliable and able to determine pregnancy in a week after fertilization.
Remember that hormonal changes in the body make themselves felt no earlier than two weeks after conception. And the effect of home pregnancy tests is based precisely on the definition of the hormone chorionic gonadotropin. It begins to develop in the female body after fertilization. Sometimes, but it is extremely rare, the chorionic gonadotropin is produced by a tumor. Then the woman will also get a positive test result. The intake of hormonal drugs containing hCG can also mess the situation up. But other drugs do not distort the results. The presence of alcohol or drugs in the body also affects the pregnancy test accuracy.
To date, with the mass production of pregnancy tests, some of them may be of poor quality. Until recently, doctors with confidence recommended such testing. But now they prefer medical examination of a woman with the help of an ultrasound.
How to Protect Yourself from a False Result of a Pregnancy Test?
To protect yourself from false result, you can use several tests from different manufacturers at once. Plus, pay attention to the messages of your body. The indicators of pregnancy include, first of all, a delay in menstruation, breast enlargement and pain, an increase in rectal temperature (more than 37 degrees), and an increase in urination. Also morning nausea and vomiting, irritability, a tendency to fatigue, a change in appetite, a desire to taste salty or sour food can also be symptoms of pregnancy.
But even these signs cannot give a hundred percent guarantee of pregnancy. Since most of them are also present before the onset of menstruation or appear with a psychological mood for pregnancy.
And still, if you do not want to give up the pregnancy test at home, since it’s relatively cheap, fast, convenient and, importantly, anonymously, you need to do it right.
First, wait for the delay in menstruation, do not rush. When choosing a test in a pharmacy, pay attention to the release date. Do not be confused by the diversity of brands, since the principle of all tests is the same. To intensify the result, do not drink a lot of liquid the night before and do not take diuretics.
Carefully read the instructions. If you still have questions, ask for advice from a consultant on a phone number, which is often indicated on the package.
If you carefully follow all instructions to the test, then the pregnancy test accuracy is guaranteed by 97% -99%.
Pregnancy Test Accuracy: Percent of Authenticity
The invention of test strips has really become a breakthrough in medicine. But over time, a wave of enthusiasm slightly decreased. Home pregnancy tests are still considered useful, but there appeared doubts about the tests reliability declared by their manufacturers. Women began to complain about false results, and gradually the percentage of authenticity of pregnancy tests began to decrease from the 99% declared in the instruction to 97%, 96%, 95%.
Attempts to evaluate pregnancy test accuracy obtained in the process of home testing have been repeatedly undertaken by different research organizations. But in practice it is not easy to do this due to the influence of a large number of objective and subjective factors on the final result of a test.
What Should a Woman Consider Before Doing a Test?
- Midstream sticks are highly sensitive and the most accurate.
- It is necessary to follow all the instructions to the test clearly, so that the results are as accurate as possible.
- Do not touch the reaction zone of the test.
- Do not allow moisture or dirt to enter the test.
- The test cannot be used after the expiration of the storage period or with obvious damage of the package (only hermetically sealed).
- Do not allow foreign matter to enter the urine sample. You cannot try to diagnose a pregnancy later than indicated on the test. This will not be a reliable result.
- It is necessary to know when to do the test, so that it is the most accurate. Remember that the level of hCG in the blood and urine reaches the maximum markings in 2-3 months of pregnancy.
- The test is most informative when conducted in the morning using the first morning urine.
- Do not use stale urine for the test.
- To increase the reliability of the results, make several tests of different manufacturers with an interval of 2-3 days.
- With an irregular menstrual cycle, the period of pregnancy may be less than expected. That’s why a test may show a false result.
- Do not forget about the first signs of pregnancy, which can already manifest and confirm your suspicions.
- You can check the test result by measuring the basal temperature. During pregnancy it exceeds 37 degrees.
Remember that there are many reasons why a test can be wrong
It should also be noted that poor health, menopause, lactation, use of alcoholic beverages and drugs (except for hCG containing drugs), as well as contraceptive methods and other factors do not affect the test results.
However, of course, the home test is not a guaranteed diagnosis of pregnancy. It does not replace mandatory examination of the gynecologist. Remember also that the test does not indicate a pathology, which is possible in the case of a blood test and ultrasound. Therefore, if you have any suspicions of pregnancy – visit the gynecologist as soon as possible regardless of the results of the home test.
If the Test Results Are Questionable
Sometimes it is not easy to interpret the results of express diagnostics: the second indicator strip is slightly outlined, shining on the inside of the test. Sometimes it happens because of low-quality production of cheap paper strip tests: when wet, the reagent becomes slightly more noticeable than in dry form.
The visible, but pale second strip most often indicates a low level of hCG, insufficient for the sensitivity of the test. In this case, it is better to postpone the test for 1-2 days or use a more sensitive option.
A strip with an insufficient degree of color may also appear as a result of improper storage of the test, violation of the instructions. In any case, repeated testing and / or a blood test for hCG is recommended.