In the practice of obstetricians, there are often cases when a woman comes to get registered for pregnancy, but the examination, which is always carried out at the first consultation, does not confirm the fact of pregnancy. It turns out that the woman just got a positive pharmacy test result. If there is no pregnancy, and the test shows two stripes, they speak of a false positive test. This is less common than false negative tests (when the test does not show a second strip during pregnancy), but still this phenomenon takes place.
What is the test's action based on?
We can only talk about false positive results after we find out how pregnancy tests generally work. This, undoubtedly, a useful invention of mankind works on the principle of a litmus test. The strip has two parts. One, called the control zone, contains no reagent. There, a strip appears when the test comes in contact with a liquid medium in the event that the test itself is serviceable, not expired, fully usable, and the presence or absence of pregnancy does not affect this strip.
In the second part of the strip there is an absorbent layer with a reagent applied to it, sensitive to the molecules of a special hormone - hCG (human chorionic gonadotropin). Such a hormone in small quantities can be in the body of non-pregnant women, as well as men, but its concentration is negligible - from 0 to 5 mU / ml.
After fertilization, the embryo descends into the uterine cavity, where it is to be implanted. Implantation usually occurs on average 7-9 days after conception (or, if it is more convenient for you to count from ovulation, then 7-9 days after it). Immediately after the ovum penetrates into the endometrium, the villi of its outer layer (chorion) begin to produce and release into the woman's blood - they connect to the blood vessels of the uterine wall - large doses of hCG. The concentration of the hormone grows evenly - every 48 hours it doubles.
First, the content of hCG in the blood increases, and then in the urine. As soon as the level of the hormone in urine exceeds the test sensitivity threshold, the reagent stains the second strip in the test zone. This will be considered a positive result.
It is recommended to start doing tests from the first day of delay, since by this time the concentration of hCG usually exceeds the sensitivity thresholds of almost all test systems. Hypersensitive tests (with a threshold of 10-15 units) can detect traces of chorionic gonadotropin even before a delay of a couple of days.
Manufacturers indicate that their products are very accurate, but in practice, pharmacy tests can often be wrong.
What does a false positive look like?
Now you need to understand what the test looks like with a false positive result. In most cases, a false positive looks like a normal positive - that is, two stripes are present. Also a false positive test can be considered questionable (or weakly positive) - the second stripe on it is less bright, it is much paler than the control one.
If a woman uses ultrasensitive test systems (the package indicates the sensitivity threshold in the range from 10 to 15 units), then the second strip may be brighter.
Another option that women often take for positive, although it is not. These are the so-called stripes - "ghosts". The second weak band may appear not after 5-10 minutes, allotted by manufacturers to assess the diagnostic result, but after 20-30 minutes, after an hour.
Usually such a strip is grayish, visible only at a certain inclination in the light. This is the same reagent that appears on the used negative test after its final drying. "Ghost" is not a reason to consider the test positive or weakly positive. He is not at all a reason to draw any conclusions.
Possible reasons
So, the test was positive, but the pregnancy was not confirmed. Someone will be pleased, but someone will be upset. But another thing is important - for what reasons the test showed two stripes. The most common reason for a false positive test is endocrine disorders in a woman's body. At the time of ovulation, something could go wrong, the follicle might not rupture, and as a result of persistence, menstruation is delayed. The same can happen with an ovarian cyst, as well as a corpus luteum cyst.
The test in this case can be either weakly positive or negative. The fact is that the molecules of some hormones are very similar in structure to chorionic gonadotropin and theoretically can be recognized by the reagent on the test system as hCG.
Often, endocrine disruptions are accompanied by a long delay in menstruation, in addition there are symptoms that resemble early pregnancy: enlarged mammary glands, there is a feeling of nausea, bloating. therefore a weak second streak is usually regarded by women as a sure sign of pregnancy.
Another reason for a false positive test could be biochemical pregnancy or frozen in the very early stages. After implantation, the embryo could die in a few days, it could be rejected by the endometrium or killed by the aggressive immune system of the female body, being perceived as an antigen. But a certain amount of hCG has already managed to get into the woman's blood and urine.
Usually, such an early termination of pregnancy generally goes unnoticed, because after a short delay, menstruation still begins. And few people attach importance to the fact that the discharge is slightly more abundant than usual. Everything is blamed on delay.
If a woman, before the delay or after it, did one or more tests, received positive results (or weak positive), but after a week such menstrual bleeding began, or the doctor did not find objective signs of pregnancy, then it is worth assuming that it is biochemical or frozen in the early stages pregnancy. HCG does not immediately decrease after the death of the embryo.
The reason for a positive test result may be the so-called residual hCG. The hormone could remain in a certain amount in the blood and urine after an abortion, miscarriage, ectopic pregnancy, which took place 1-2 cycles ago.
In the absence of pregnancy, the test can also become positive due to the presence of certain neoplasms (hormone-dependent tumors).
That is why it is very important to visit a doctor in any of the cases described above.
Often, women are interested in whether the drug taken for the treatment of infertility can affect the test result. Treatment for infertility is different. If a woman was stimulated to ovulate with hormonal drugs, then to rupture the follicle she was injected with hCG in an injectable form once. And traces of this injection in the blood and urine will be present for at least 12-14 days or even more (it all depends on age, metabolism). In this way, the test will in any case show a positive result, regardless of the fact of pregnancy.
If a woman is prescribed progesterone drugs for the treatment of recurrent miscarriage, to increase the likelihood of conception and implantation if the second phase of the cycle is insufficient, then such drugs do not in any way affect the level of hCG in the body. This means that when taking "Utrozhestan" or "Duphaston", the test results are not distorted by medications.
If pregnancy occurs in the IVF treatment protocol, then the tests may show a false-positive result rather than a false-negative one, this means that against the background of hormone therapy that a woman has received and is receiving, the test may be positive in the absence of a result from embryo transfer.
Often, pregnancy tests are mistaken not only with hormonal disruption, but also with breastfeeding. It is believed that a breastfeeding woman cannot get pregnant. This statement has already made many many children, because the cycle is restored not on schedule, not on command, but with a decrease in the level of the hormone prolactin and an increase in progesterone. When the ovaries begin to function again, when the egg starts to ripen, you can't guess.
Sometimes it is enough to introduce complementary foods to a baby who previously ate only a breast - prolactin falls, and the cycle is restored imperceptibly for women. Accordingly, pregnancy is possible. But against the background of still overestimated prolactin, a pregnancy test can show erroneous both false-positive and false-negative results.
Well, how not to mention such a reason as errors during the test. Of course, more often errors lead to false negative results, but it happens the other way around. It is very important to adhere to the instructions: do not overexpose the test in urine for longer than the specified time, do not wait for half an hour to get a result (the waiting time for the "response" is usually recommended by the manufacturers and ranges from 5 to 10 minutes). Anything that can appear on the strip after 10 minutes is invalid data, which cannot be regarded as a test result at all.
What to do?
If the pregnancy, which the test showed, was not confirmed by an ultrasound scan or a gynecologist, then it is very important to establish why the woman is having a delay in menstruation. It is possible that the reasons lie in hormonal disorders, dysfunction of the hypothalamic-pituitary system of the brain, ovarian dysfunction, early menopause, inflammatory or non-inflammatory diseases of the reproductive system.
It is also important to visit an oncologist and do a blood test for tumor markers: perhaps an increased level of chorionic hormone is one of the early symptoms of the oncological process.
If the test showed positive results, and then heavy menstruation began after a delay, it is also important to consult a gynecologist and do an ultrasound of the pelvic organs, do general blood and urine tests, a blood test for hCG in dynamics - this will help to find out if there was a pregnancy at all. If so, it is important to try to establish the causes of fetal freezing. This will help you get the right treatment and plan your next pregnancy responsibly. If not, a general examination by an endocrinologist, gynecologist and oncologist is also indicated.
The tests are very convenient, inexpensive, and easy to use. But if you need to get more accurate results, it is worth visiting the clinic and do a blood test for hCG (it is inexpensive and costs from 300 rubles). It will allow you to establish the exact quantitative content of hCG, track the dynamics of its growth or decrease, and also determine pregnancy even before menstruation 3-4 days.
The probability of error in such a study is extremely low, which cannot be said about tests.
