Modern pharmaceuticals provide a woman with the opportunity to use testing devices to independently find out whether she is pregnant or not. Gynecologists call this simple test one of the most reliable ways to determine at home whether a woman is expecting a child. But for some reason it happens that the test gives a false result. What causes errors?
How does a pregnancy test work?
When an embryo is implanted in a woman’s body after fertilization of an egg, a certain hormone appears in her blood and, accordingly, in her urine - human chorionic gonadotropin (hCG). To detect it, a small strip of specific immunoglobulins - sorbed antigens labeled with colloidal gold - is industrially applied to a piece of paper. When antigens come into contact with urine, a reaction occurs. If the hormone is present in the liquid, then visually it appears in the form of a red thread. If there is no hCG, or its amount is negligible, then only one control strip is visible on the test, indicating that the system is working. But if the test is so simple and clear, why does it sometimes fail?
Simple mistakes
The reasons for erroneous pregnancy test readings can vary. For example, the expiration date of the product itself, violation of the temperature regime during its storage or transportation, as well as improper use. According to the instructions, to obtain accurate data, a woman’s daily or better morning urine is required; it is in it that human chorionic gonadotropin is concentrated.
An incorrect reaction from the test device may occur if the hormone level is insufficient if the egg is fertilized, but the embryo has not yet attached to the wall of the uterus. Usually this process occurs after the seventh day of conception, and only then does hCG, created by nature for the normal development of the placenta, begin to be released. However, it also happens the other way around: the test shows the presence of pregnancy, but this is not detected during a gynecological examination.
Reasons for false positive test results
The method of detecting hCG using a reaction to specific immunoglobulins is used in medicine in the laboratory diagnosis of many infectious diseases and hormonal disorders. In particular, a pathology such as chorionepithelioma can also be confirmed positive test for pregnancy, although this disease is classified as oncology.
Human chorionic gonadotropin is present in a woman’s body for some time after a recent abortion or miscarriage. This hormone is also included in some fertility drugs, and for this reason the test may also show a positive result, although in fact there is no pregnancy.
If the study clearly reveals the presence of hCG, and a gynecological examination does not detect an enlarged uterus, then this is a clear sign of an ectopic pregnancy. This means that the fertilized egg has implanted in the fallopian tube and emergency surgery is required. So it happens that a test at home saves a woman’s health and even life.
False Negatives
Cases when there is no red line on the test, but pregnancy develops in the meantime, are extremely rare. This is usually due to a problem in the urinary system. For example, chronic kidney disease often leads to severe disturbances in excretory function. Then the concentration of hCG in the urine is seriously reduced, even if the level of this hormone in the blood is increased.
Large intake of fluids or diuretics before the test is also likely to change the result in negative side, since human chorionic gonadotropin will be rapidly washed out.
In atypical diseases, such as anorexia, there is often a decrease in the production of various sex hormones. In this case, a woman may become pregnant, but the level of hCG in the urine in the first three to four weeks is usually insufficient to confirm this using a standard test. And in this case, whether a woman is expecting a child can only be found out from a gynecologist.
It should also be remembered that alcohol, fatigue, stress, lactation, taking any non-hormonal medicines, and also birth control pills the test results are not affected in any way.
If all your knowledge about pregnancy tests is limited to stories about “two lines”, then this article is what you need..
What is a pregnancy test and how does it work?
Pregnancy tests look for a substance called human chorionic gonadotropin (hCG) in the blood or urine. This hormone begins to be produced at the very moment when the fertilized egg attaches to the wall of the uterus.
This usually - although not always - occurs six days after conception. If pregnancy occurs, the level of hCG begins to rise extremely rapidly, doubling every two to three days.
What pregnancy tests are there?
In general, they can be divided into two groups: blood and urine tests.
You can perform a urine test not only in a medical office, but also at home. These rapid tests are simple and convenient. To achieve the most reliable results, carefully follow all the rules described in the instructions.
Blood tests are carried out only in medical institutions. This method allows you to detect pregnancy at a very early stage, but for obvious reasons you need to wait longer for results than with a urine test.
Blood tests for hCG are of two types:
1) Qualitative test - states the presence or absence of hCG in the blood. In fact, it only gives an answer to the question “Are you pregnant?”
2) Quantitative test (beta-hCG) measures the exact amount of the hormone in the blood. The sensitivity of this test is extremely high. Knowing the exact concentration of this hormone makes it possible to monitor problems that arise during pregnancy. In addition, this test is absolutely necessary to diagnose an ectopic (tubal) pregnancy.
How accurate are pregnancy tests?
To reliably determine pregnancy, you must wait at least ten days after the delay. It is advisable to carry out the test in the morning, when the urine is most concentrated.
Home rapid pregnancy tests are approximately 97% accurate. The following factors may influence this indicator:
1) Carefully follow all instructions.
2) Timing of ovulation and implantation of the egg into the wall of the uterus.
3) Suitable choice deadline for the test.
4) Sensitivity of a particular test.
Price of the test and difficulties in using it
You can buy a pregnancy test at any pharmacy without a prescription. The price depends on the manufacturer. For the most part, they are inexpensive: the price range varies from 80 to 800 rubles, rarely more.
Using home tests is usually straightforward. The most convenient tests are those that can be held directly under a stream of urine, but there are other options: some strips are prescribed to be placed in a glass of urine, while others need to be dripped with a pipette.
Be that as it may, after contacting the urine with the strip, you need to wait a few minutes to get the result. The latter may appear as a stripe, a change in color, or through symbols (for example, “+” or “–”). They also sell advanced digital tests that will delight you with the word “Pregnant” on the display.
How to interpret test results
It is important to know what positive and negative pregnancy test results mean.
If the result positive, that means you are pregnant. And it doesn’t matter how faded the stripe, symbol or sign is. In rare cases, there are so-called conditionally positive results: when, according to the test results, pregnancy has occurred, which in fact is not true. Such errors may be associated with the presence of protein or blood in the urine, as well as with the use of certain drugs (tranquilizers, anti-convulsants and others).
Negative the result means that you are most likely not pregnant. However, the opposite is also possible if:
1) the test strips have expired,
2) you violated the operating rules,
3) you performed the test too early,
4) your urine is too dilute because you drank a lot of water the day before,
5) you are taking certain medications (for example, diuretics and antihistamines).
If you get a negative result, just in case, repeat the test in a week to be sure.
If you get different results after taking multiple tests, contact your doctor. It may be time to do a blood test for hCG.
From the moment the egg attaches to the uterus, the woman’s body receives information and begins preparing for it. The work of many organs is restructured under the influence of hormones, which begin to be produced more actively. The level of human chorionic gonadotropin, or hCG, the hormone used to determine pregnancy, is constantly increasing. The tests are based on assessing the amount of this particular substance in a woman’s urine - if its level exceeds the norm for a non-pregnant woman, then the test shows a positive result, which indicates that the woman is most likely pregnant.
Pregnancy tests are convenient in that they can be carried out in the UK and do not require special equipment. They are reliable compared to other home methods of determination. Tests from different manufacturers have different sensitivity: when some cannot yet due to too early date and a small amount of the hormone, others already show distinct red stripes.
Most tests guarantee almost exact result already from the first day of the delay, but you need to understand that the hormone accumulates gradually, and its concentration in the urine is much lower than in the blood, therefore, the more time passes from the moment of conception, the more accurate the result will be. For accuracy, doctors recommend a test ten days after the delay.
A pregnancy test should be done in the morning, when the concentration of various substances in the urine is increased.
When is a false pregnancy test result possible?
When buying a test, check its expiration date - if it has expired, you cannot hope for an accurate result. The test can lie if it is not done according to the instructions. Read all package directions carefully and follow them carefully. For reliability, use two or three tests from different companies.
Pregnancy tests can show false-positive and false-negative results, with the latter cases being much more common. A negative result during pregnancy is an indication that the level of hCG in the urine is still insufficient for the test to detect it. This happens if conception occurs a few days before the expected start of menstruation.
If you drink a lot of water before the test, the concentration of the hormone in the urine will decrease, and the test may also show a negative result.
A positive result in the absence of pregnancy occurs very rarely and is associated either with poor-quality products or with health problems when taking certain medications that cause increased level HCG in the body. This may also be a sign of an ectopic pregnancy and a threatened miscarriage.
Modern pharmaceuticals provide a woman with the opportunity to use testing devices to independently find out whether she is pregnant or not. Gynecologists call this simple test one of the most reliable ways to determine at home whether a woman is expecting a child. But for some reason it happens that the test gives a false result. What causes errors?
How does a pregnancy test work?
When an embryo is implanted in a woman’s body after fertilization of an egg, a certain hormone appears in her blood and, accordingly, in her urine - human chorionic gonadotropin (hCG). To detect it, a small strip of specific immunoglobulins - sorbed antigens labeled with colloidal gold - is industrially applied to a piece of paper. When antigens come into contact with urine, a reaction occurs. If the hormone is present in the liquid, then visually it appears in the form of a red thread. If there is no hCG, or its amount is negligible, then only one control strip is visible on the test, indicating that the system is working. But if the test is so simple and clear, why does it sometimes fail?
Simple mistakes
The reasons for erroneous pregnancy test readings can vary. For example, the expiration date of the product itself, violation of the temperature regime during its storage or transportation, as well as improper use. According to the instructions, to obtain accurate data, a woman’s daily or better morning urine is required; it is in it that human chorionic gonadotropin is concentrated.
An incorrect reaction from the test device may occur if the hormone level is insufficient if the egg is fertilized, but the embryo has not yet attached to the wall of the uterus. Usually this process occurs after the seventh day of conception, and only then does hCG, created by nature for the normal development of the placenta, begin to be released. However, it also happens the other way around: the test shows the presence of pregnancy, but this is not detected during a gynecological examination.
Reasons for false positive test results
The method of detecting hCG using a reaction to specific immunoglobulins is used in medicine in the laboratory diagnosis of many infectious diseases and hormonal disorders. In particular, a pathology such as chorionepithelioma can also be confirmed by a positive pregnancy test, although this disease is classified as oncology.
Human chorionic gonadotropin is present in a woman’s body for some time after a recent abortion or miscarriage. This hormone is also included in some fertility drugs, and for this reason the test may also show a positive result, although in fact there is no pregnancy.
If the study clearly reveals the presence of hCG, and a gynecological examination does not detect an enlarged uterus, then this is a clear sign of an ectopic pregnancy. This means that the fertilized egg has implanted in the fallopian tube and emergency surgery is required. So it happens that a test at home saves a woman’s health and even life.
False Negatives
Cases when there is no red line on the test, but pregnancy develops in the meantime, are extremely rare. This is usually due to a problem in the urinary system. For example, chronic kidney disease often leads to severe disturbances in excretory function. Then the concentration of hCG in the urine is seriously reduced, even if the level of this hormone in the blood is increased.
Large intake of fluids or diuretics before the study is also likely to change the result in a negative direction, since human chorionic gonadotropin will be rapidly washed out.
In atypical diseases, such as anorexia, there is often a decrease in the production of various sex hormones. In this case, a woman may become pregnant, but the level of hCG in the urine in the first three to four weeks is usually insufficient to confirm this using a standard test. And in this case, whether a woman is expecting a child can only be found out from a gynecologist.
It should also be remembered that alcohol, fatigue, stress, lactation, taking any non-hormonal medications, as well as birth control pills do not affect the test results in any way.
Time: 12:09 Date: 18/04/02
Help me figure it out! I am 1.5 weeks late (this has never happened before) and there are no signs of my approaching period either. I took three different rapid tests to determine pregnancy, but the result was zero (that is, the tests show that there is no pregnancy. Is it possible that the tests are showing incorrectly?
Time: 13:06 Date: 18/04/02
It's very possible. I didn’t show anything until the 6th week, I already went to the gynecologist and she manually felt everything there, that there was a pregnancy, but he still gave a negative result.
Time: 13:16 Date: 18/04/02
obychno HOROSHIE pesty ne vrut. u menja opredelili na sroke kogda betta byla 29(nu ochen" malen"kaja)
Time: 13:19 Date: 18/04/02
They're still lying. It is usually believed that they lie in the direction of not showing pregnancy if it is present, but here on an old forum one girl wrote that her husband’s pregnancy test was positive.
In order not to suffer and not to guess whether the test is lying or not, it is better to take a BLOOD test for hCG. The most accurate thing that can be.
Time: 16:25 Date: 18/04/02
As a doctor once explained to me, the test can be negative in the presence of pregnancy if the deadline for determining it is missed. Simply put, on the first day of the delay the test would be positive (if there is a pregnancy), and after a few days the test will persistently show 1 line.
I don’t know how true this is, because... I always went to the doctor to calm myself down, which I advise you to do.
Time: 17:37 Date: 18/04/02
It may well be, although for me personally the pregnancy was discovered precisely by a test. On the other hand, my pregnancy period was then 10 weeks, no less, but my doctor definitely confirmed the pregnancy.
Time: 08:11 Date: 19/04/02
Tests can lie (in the direction of denying pregnancy). Fertilization of the egg by the sperm occurs in the fallopian tube, after 14 days (for each woman individually, it can take a month) the fetus enters the uterus, after which a hormone begins to be produced, to which the 2nd strip in the test reacts, and only then can we say, that the woman is pregnant, although all this time she was already in an “interesting” position. If the tests do not show pregnancy, then you should not postpone the visit to the gynecologist for a long time. But delays can also be caused by stress and changing belts. How is your general condition? I knew that I was pregnant within a week without any tests, so much and in such quantities, I never wanted condensed milk.
Time: 09:16 Date: 21/04/02
They can, they can lie! How about
Time: 21:50 Date: 22/04/02
And I have tests for 3 months. showed pregnancy, ultrasound showed its absence. As a result, it turned out to be a bad disease. Sorry, I'm not scaring, I'm just sharing my experience.
Time: 11:51 Date: 23/04/02
They didn't lie for 4 years. If there are any violations, the 2nd stripe may actually blink.
And so far they haven’t lied. Even a month ago - there was a delay of more than a week - the test stubbornly showed “no”, I no longer believed it, and suddenly M...
Time: 13:58 Date: 23/04/02
Go to the doctor. They will do a blood test or look at an ultrasound and they will determine everything: whether you are pregnant or not. Because if there is no pregnancy, a cycle failure for such a long period of time is not a very good sign. I couldn’t stand so much time in uncertainty; I would have run away long ago.
Time: 13:40 Date: 27/04/02
And I have a funny thing about this - quite often I donate blood to the Central Clinical Hospital laboratory, where they check it for everything and they always tell me that I’m pregnant) Although special. They don’t do a test, but speak based on some of their characteristics.
Time: 15:44 Date: 28/04/02
I have a lot of experience with express tests; I’ve been doing them for five years. They have never let me down. With long delays, I did it 100 times, it always showed no pregnancy. And when I became pregnant, I found out about it precisely from an express test.
In my opinion, the main thing is to do it right:
- preferably use morning urine,
-evaluate the result in 1-5 minutes, and not 10-20, because after 10-20 minutes the second strip usually always appears,
- and remember that even the faintest second line (maybe barely visible) means that you are pregnant
By the way, when I was in the hospital, doctors, if they urgently needed to determine pregnancy, also used them.
Time: 09:09 Date: 08/05/02
Very rarely. In healthy women with normal hormone levels good tests They practically don’t lie. You can take a blood test for hCG, do an ultrasound - this is to make sure.
Time: 22:26 Date: 10/05/02
Since the moment of pregnancy, I took the test 6 times within a month (“Be sure”) and it never showed pregnancy. This only became clear when I went to the doctor. And somewhere in the second month, the test showed a weak second line. Like this.
Time: 14:06 Date: 20/05/02
By the way, I took a test yesterday and it was negative. I’m 6 days late, and last month I didn’t have my period at all, but I went to the doctor and said that there is no pregnancy. But I also didn’t find any diseases related to the lack of periods, she says the cycle needs to be stabilized and she prescribed hormones, but I don’t take them . This time, while I’m waiting, I don’t know the signs of pregnancy, so I don’t see them, but there seem to be no signs of menstruation. So. I don’t know what to do..maybe already)))I hope....
Time: 04:05 Date: 29/05/02
Three in a row is unlikely. Maybe I should wait for an ultrasound?
Time: 21:56 Date: 04/06/02