Should you trust pregnancy tests?

Today, manufacturers offer a huge selection of home rapid pregnancy tests, which allow you to find out about the position 7-10 days after conception. Such early diagnosis and accuracy are ensured by the reagents with which the test strips are impregnated. However, sometimes it is difficult to distinguish a reliable strip from a reagent, and the result may be interpreted incorrectly.

Many women even post photos of their tests on forums and ask to evaluate the results, but in this case it would be much more effective to purchase a better test and take a blood test.

How does a pregnancy test work?

Pregnancy tests are sensitive stickers impregnated with a special reagent, which, if a woman has a hormone secreted during pregnancy in her urine, responds with the appearance of a second red stripe. This hormone (hCG) is produced 6-8 days after fertilization and its concentration in the blood and urine increases exponentially, which indicates a normally developing pregnancy.

This fact also explains the difference in the tones of the 2nd strip in the tests, which can be very weak at first, and then become bright red. In the absence of pregnancy, the hCG level in a woman’s blood does not exceed 5 mIU/ml and tests do not react to it in any way.

Pregnancy tests: percentage of reliability

The invention of test strips was truly a breakthrough in medicine. But over time, the wave of enthusiasm died down slightly. No, the test systems more than justified themselves, but doubts began to arise about the reliability declared by their manufacturers. Increasingly, women began to complain about receiving false results, and gradually the percentage of reliability of pregnancy tests from the 99% stated in the instructions began to modestly decrease: 97%, 96%, 95%.

Attempts to assess the reliability of the results obtained during home testing have been made repeatedly by various research organizations. But in reality, it turned out to be difficult to implement this idea due to the influence of a large number of objective and subjective factors on the final test result.

In general, the researchers agreed that the accuracy of modern tests is quite high, but it is slightly lower than stated in the instructions. According to some data, approximately 16% of them are able to determine pregnancy on the first day of the delay, but already on the 3rd day of the delay, the vast majority of pharmacy tests will cope with the task.

Meanwhile, firstly, even such a reliability of the result is very high, and secondly, most often it is not so much the test itself that is to blame for obtaining false data, but other circumstances.

The principle of operation of the reagent in tests

Express tests vary in modifications and prices.

There are these types:

• strip strip;
• jet;
• tablet.

The reagent on a pregnancy test (photos of a false positive result are presented in the article for clarity) most often appears on cheap test strips, the production of which uses a cheap chemical reagent.

For each type of test, the manufacturer provides instructions for use, violation of which may also result in incorrect results.

Strip strip

1st generation products include strip tests produced in the form of strips. They are intended for independent individual use and obtaining quick results. In terms of cost, such tests can be either very cheap (for example Itest) or more expensive (Evitest, Frautest). Strip tests are paper-plastic strips that have an inner layer impregnated with a reagent. Upon contact with urine in a certain area, 2 vertical lines appear on the strip.

One of them confirms the validity of the test and always appears if the reagent is of high quality and the procedure was carried out according to the instructions. The appearance of the 2nd line just depends on whether the woman is pregnant or not, and whether the hormone hCG (human chorionic gonadotropin - secreted by chorionic tissue 6-8 days after embryo implantation) is present in the blood. If vertical lines do not appear on the test at all (and this also happens), this indicates that the product may be expired or the reagent in it has been destroyed for some reason (external influence, manufacturing defect).

The reagent on a pregnancy test, a photo of which can be shown to the gynecologist if questions arise, most often appears on simple test strips, especially those from the cheap price category. Such stripes resemble a “ghost” and often mislead girls and women. Also, a fuzzy reagent strip can often appear when even expensive and high-quality tests are used incorrectly.

To get a reliable result when using test strips, you should follow some rules prescribed in the manufacturers' instructions:

• the maximum concentration of the hCG hormone is observed in the first morning urine, which is what needs to be collected to obtain the most reliable analysis;
• before collecting urine, hygiene procedures should be carried out, since non-compliance with hygiene can distort the results;
• the container for collecting urine must be clean;
• The test strip should be immersed in the biomaterial strictly to the mark indicated on the test, and kept in it for the amount of time specified by the manufacturer (usually 20-30 seconds);
• after this, the test should be placed horizontally on a clean and dry surface;
• Results can be assessed after 1-10 minutes; the specific time depends on the manufacturer and the sensitivity of the test.

You should also know that the intensity of coloring of the control strip depends on the gestational age - the longer it is, the brighter the second stripe will be, and vice versa.

Tablet

This option is a strip with a reagent, which is placed in a plastic tablet with two windows, into one of which a few drops of urine are introduced using a pipette. After a few minutes, the result will be visible in another window - depending on the manufacturer, it can be either two red lines or stripes, or a plus or minus sign. The operating principle of tablet-type tests is the same as strip strips - when a certain part of the test containing the reagent interacts with urine, a chemical reaction occurs and the level of the hCG hormone is determined.

The reagent on a tablet-type pregnancy test (photos with false and questionable results of this type of test are presented later in the article) can also appear, but this happens less often, since these tests are more expensive and manufacturers care more about their quality.

To minimize the appearance of reagents and erroneous results in many tests of this type, the volume of the required amount of liquid (urine) is strictly dosed using the supplied pipette, and the area where the urine directly enters is limited by a special window. Also, most tests of this type include a clean container for collecting biomaterial.

Jet

Perhaps the simplest and most convenient to use are inkjet tests. For pregnancy detection products of this type, there is no need to collect urine in separate containers or use a pipette - you just need to place the test under the stream while urinating for 10-15 seconds. and then evaluate the result after the time specified in the instructions. Outwardly, such tests resemble tablet tests - the strip with the reagent is enclosed in a plastic case, but it is much easier to use, which allows you to quickly find out the result, if necessary, not only at home.

Also, these types of tests are characterized by the highest sensitivity and are able to determine pregnancy 5-7 days before the expected menstruation. In the description of such tests, manufacturers indicate that they are ultra-or supersensitive and determine the level of the hCG hormone in the blood even at its very low concentration.

Possible mistakes when performing a pregnancy test

Using this method, it is possible to determine pregnancy only on the tenth to twelfth day after the day of conception. Therefore, initially you need to wait until your period is missed and only then carry out the test. Carrying out the test at an earlier period will give an erroneous result. It happens that due to inaccuracies in following the methodology (it is given in the instructions for each test), transportation and storage features, some tests show a reliable picture only after seven to ten days of delay. Thus, it is not enough to do a test on the second day of the delay; you need to do it again after five to seven days, and to ensure accuracy, do a blood test for hCG .

For women suffering from kidney diseases, renal arteries, renal failure, vegetative-vascular dystonia, arterial hypertension, aortic atherosclerosis, heart failure and other diseases accompanied by circulatory disorders in the kidneys, the test may initially show a false negative result. If they suspect pregnancy, they should do a repeat test in a week.

It is necessary to strictly follow the test instructions contained in the insert. It is advisable to follow the time recommendation: carry out the test in the morning, in a fresh portion of urine, immediately after urination. If it is not possible to carry out the test in the morning, you can do it in the afternoon, but without visiting the toilet for four hours. Pregnancy can only be diagnosed after five minutes. After more time, the result will not be reliable. Blood or saliva cannot be used to perform the test; the tests are designed to work with urine only.

How does the reagent manifest itself?

The principle of operation of all of the above tests is the same - when urine gets on part of the strip soaked in the reagent, the reagent begins to appear in the form of dark red stripes. If there is pregnancy, then 2 stripes appear, and if there is no pregnancy, then only one control strip. This technique is based on determining the presence of an increased level of hCG in the blood and is visually expressed in the fact that when these antibodies interact with a chemical indicator, the bands become colored.

In modern, even simple tests, in the presence of pregnancy, the second line appears very quickly, sometimes even faster than the control line, which is always present. However, in some simple strip tests, a reagent may appear in place of the strip indicating pregnancy, misleading girls and women.

Pregnancy test reagent. The photo shows how the test works.

This streak may appear slightly gray or pinkish and may change color as it dries. As a rule, it is very pale and barely noticeable. Sometimes some girls may take this result as a positive confirmation of pregnancy, which is not always true.

The reagent especially often gives a false positive result when using tests in the cheapest price segment.

Pregnancy tests

Pregnancy tests, which are sold in pharmacies, are designed for the reaction of traces of hCG with specific antibodies. Antibodies are applied to the test strip. Biological fluid (urine) is applied to the test, which has two strips: one of them is a control strip and the reaction is always visible on it. On the second, an immunoenzyme reaction will occur if there is hCG in the test liquid. In its presence, the liquid will turn pink. If during the test not a single strip is colored, this means that the test itself is defective. When purchasing a test, you should always check the expiration date and purchase it only at a pharmacy.

Sensitivity of pregnancy tests

The sensitivity of pregnancy tests is determined in mIU/ml. Different companies produce pregnancy tests of varying sensitivity.

Most often you can find tests on sale with an hCG susceptibility indicator of 25 mIU/ml. This is due to the fact that by the time the delay occurs, the concentration of this hormone in the bloodstream just exceeds this indicator. When purchasing a pregnancy test, you should pay attention to its sensitivity and type. Conventional test strips have low sensitivity. They show pregnancy no earlier than 2 weeks after conception.

Tablet-type tests have average sensitivity and can be informative until a delay, but modern inkjet tests, which are capable of recording even minor levels of the hCG hormone in the blood (from 10 mIU/ml), have the greatest sensitivity.

When testing, it is important to know that the hCG hormone does not appear in the blood and urine immediately after the moment of conception (the actual fusion of male and female reproductive cells) and not even immediately after the successful implantation of the fertilized egg into the uterine cavity, but begins to form 2 days after this. That is why carrying out pregnancy testing before 7 days after the expected conception does not make sense.

Reliability of pregnancy tests according to doctors

So, doctors conducted a small online survey and found that in hundreds of cases, when determining pregnancy, women received false results.
And most often due to the fact that they ignored advice about the optimal ten-day period from the day of fertilization of the egg. Before this time, according to doctors, it is unrealistic to get a reliable result. Even with urine tests, doctors cannot accurately confirm pregnancy before 14-16 days after ovulation. An exception to the general rule can only be those women with a shortened cycle, the second phase of which is less than two weeks.

What does a used test strip look like if you are pregnant?

If pregnancy is present, the test confirms this fact by the appearance of 2 red lines on the strip at once: in the test and control zones. The stripe, which confirms the fact of pregnancy, can be either very weak and light pink, or brighter, which depends on the gestational age and the level of concentration of the hCG hormone in the bloodstream. If a woman uses a more advanced version of the test (digital), then a “+” sign or the word “pregnant” will appear in the control zone, and the due date may also be indicated.

When using conventional test strips, carrying out the procedure every other day, you can track the dynamics of the change in color saturation of the 2nd strip, which will become brighter each time. This indicates that the level of the hCG hormone in the blood increases and pregnancy develops without pathology.

How do rapid pregnancy tests work?

To understand why the test does not show pregnancy when it already exists, you need to know the principle of its operation, which is directly related to the processes occurring in the body of a pregnant woman.

Conception occurs at the moment of fusion of the egg and sperm. The fertilized egg begins to rise into the uterine cavity to be implanted into its wall. As soon as the future embryo is implanted into the uterine wall, changes begin to occur in the woman’s body that will be aimed at maintaining the pregnancy.

HCG is found in both the blood and urine of a pregnant woman. The amount of a substance is usually denoted by the unit of measurement mIU/ml (international units per milliliter).

Tests from different companies show the presence of pregnancy in their own way: it can be 2 stripes, a “+” sign or the word “pregnant”. But regardless of how the test strip is designed, it will show a positive result only when it interacts with the hormone, and it must reach a certain level. The concentration of hCG in the blood and urine varies significantly: the hormone rises more slowly in the urine. Its level doubles approximately every 2-4 days.

Most modern pregnancy tests have a sensitivity of 20-25 mIU/ml. This amount of hCG in the urine will be achieved approximately 11-14 days after conception. We must not forget that conception occurs on the day of ovulation or in the first days after it, and ovulation itself occurs approximately in the middle of the cycle. Thus, the optimal level of hCG for detection will be reached just in time for the expected start of a new cycle. That is why it is recommended to take a pregnancy test no earlier than 1 day of delay. Otherwise, manufacturers do not guarantee that the test strip will show pregnancy even if it is present.

By the way, rapid tests using urine are informative only in the early stages. If the pregnancy is more than 8-9 weeks, the test does not show pregnancy, because the hCG level begins to decrease during this time for natural reasons.

How to distinguish the reagent from the second strip?

The reagent on a pregnancy test can mislead a woman. Photos of such ghost stripes can be found on many women's forums.

Indeed, in the early stages, especially when testing before a delay, tests can produce weakly positive results, which should not be confused with the reagent:

• the reagent appears in the place where there should be a strip during pregnancy, but it remains white;

  

• sometimes the reagent may spread in an uneven pink spot across the strip;
• the reagent may also be gray in color;
• even the weakest strip will be vaguely similar to the control strip, in contrast to the reagent, which has a completely different tone;
• if you repeat the test the next day, the real line will become brighter, which will indicate pregnancy, but if it was a reagent, then the line will not become brighter.

On a pregnancy test, the second line is white

A white line on the test may not be the most joyful news for a woman, because determining pregnancy using a test purchased at a pharmacy has always been the easiest way that does not require wasting time and money. Every lady has heard about this method, it is quite easy to use and quite accurate, but it happens that the results of the test make you wonder: what could this mean? And where does this white stripe on the test come from? what should I do? Today we will try to answer these and other questions.

There are currently an abundance of tests, but, unfortunately, quality does not accompany every package. Sometimes the tests are wrong, sometimes they aren’t, and sometimes they just drive you into a blind corner. For example, a white line appears on a pregnancy test. All that remains is to come to terms with unscrupulous manufacturers and learn how to choose and use express tests, as well as decipher them.

What determines the accuracy of the test?

In order to avoid false results when carrying out the procedure for determining pregnancy at home using tests, it is important to follow certain rules:

• the test should be removed from the sealed package immediately before the manipulation;
• the container for collecting biomaterial must be clean and dry (it is better if it is a pharmaceutical container);
• when immersing the dough in the collected urine, it should be kept in it for the specified amount of time so that it can be sufficiently saturated;
• urine should not in any way come into contact with the area where the results are reflected;
• the use of diuretics (medicines or herbs) or excessive fluid intake may affect the test results, since in this case the urine will be very dilute and the concentration of the hCG hormone will be lower;
• testing is most effective after waking up in the morning, since more of the hormone is concentrated in the urine during the night;
• You should be aware that tests have expiration dates, and using an expired test may affect the result.

The result should be assessed after the time specified in the instructions - usually from 3 to 10 minutes. In general, self-use of rapid tests usually does not cause difficulties for most women and helps them reliably find out about pregnancy in 98% of cases.

What does a weak second line mean?

Sometimes when testing, a fuzzy second line appears in the test area. If this streak is not a reagent, which usually spreads or turns gray after drying, then most often it indicates that new life has arisen inside the woman. In this case, you should repeat the test the next day - it should become brighter and the strip itself will be visible more clearly. If there is no dynamics, you should consult a doctor, as this may be a sign of an ectopic or non-developing pregnancy.

Also, sometimes a positive pregnancy test with faint stripes can be associated with certain diseases of the internal female genital organs (ovaries or uterus), in which the hCG hormone is also released.

Modern pregnancy tests allow women to find out about their condition very early, even before a delay occurs. Any woman can find a lot of information on the Internet about how to perform the test correctly, how the reagent behaves under the influence of the hCG hormone, and what photos of positive tests look like. However, despite the fact that the accuracy of tests today is very high, only an ultrasound and blood test can definitively confirm pregnancy.

What to do if the pregnancy test is positive

Even if the child is long-awaited, there is no need to rejoice wildly. The first test can be wrong because all tests can be wrong.

What to do next? Pull yourself together and wait for the symptoms of pregnancy to appear or do a repeat test after 2-3 days. If the second diagnosis confirms the initial result, you need to contact a gynecologist, take a blood test for hormones and after 3-4 weeks undergo an ultrasound, without which it is impossible to get a 100% correct answer.

The doctor may prescribe an ultrasound examination earlier if there are prerequisites for this - brown or bloody discharge, pain in the lower abdomen or side.

If the situation is confirmed, it is necessary to register with a gynecologist, who will monitor the entire period of gestation.

What actions to take if you have an unwanted pregnancy? It happens that even after using contraceptives, for example, after Postinor, women become pregnant. This happens either due to a low-quality drug, or if the drug was taken at the wrong time (conception has already occurred).

Should I continue the pregnancy in this case? The decision is made by the woman, and only she. It is worth taking into account age, existing pathologies and much more, which can cause infertility or problems with pregnancy in the future if you have an abortion now.

In any case, there is no need to panic as it may just be a test error. Therefore, after a while it is better to repeat the study or get tested for hCG levels.