Too often, they show negative results when the woman is already in position.
Do you know how many pregnancy tests are sold in Russia per year? Over 30 million! Women rightly believe that popping into a pharmacy and then going to the toilet is much easier and faster than taking a blood test for hCG (human chorionic gonadotropin, a hormone that is produced from the first days of pregnancy) or making an appointment with a gynecologist and for an ultrasound scan.
It would seem that everything is simple here: one strip – you are not pregnant. Two – congratulations! However, if you read the instructions for the tests, they all warn: the results can be both false positive and false negative. Doctors add: it turns out that mistakes happen more often than they thought. Studies that have been conducted over the past ten years at the University of Washington School of Medicine in St. Louis prove that at least five percent of cases, tests do not show women that they are pregnant.
“About ten years ago, a pregnant woman came to the emergency room with a threatened miscarriage,” Ann Gronowski, professor of obstetrics and gynecology at the Barnes-Jewish Hospital at the University of Washington School of Medicine, recalls how the study began. “But when we gave her a rapid test, it came back negative. Whereas a blood test and an ultrasound scan confirmed the presence of pregnancy. “
After some time, a similar situation was repeated with another patient. Then a colleague shared another case with Ann. Some statistics began to emerge. And the doctors began research. It turned out that tests can lie not only in the first two weeks of pregnancy (manufacturers honestly write about this in the annotations and advise to repeat the test in a few days), but even after five to six weeks, when the concentration of hCG in the urine is very high.
“The first strip of test just shows it is working fine. The second occurs when a substance in the test strip reacts to a hormone, explains Granowski. “But urine can also contain“ damaged ”forms of the hormone. They are called fragments of the hCG nucleus. And in some cases, the substance from the test strip will accidentally react to them. Moreover, the longer the gestation period, the more these fragments become. And the greater the likelihood of an error in the test. “
Ann says that during the experiment, they tested 11 of the most popular pregnancy tests in women. Two of them showed erroneous results very often, seven more – from time to time. And only two tests have never been wrong.
“The most inaccurate test has been negative in five percent of our pregnant patients,” Granovski complains. “And, as luck would have it, it was exactly the test we used for the initial admission.”
However, there was also a polar case. The girl bought a test before the vacation and saw two strips. She was a little upset, because on vacation she planned to have a full blast – she was going to Disneyland. And I had to lead an exemplary lifestyle so as not to frighten the pregnancy, because the first weeks are the most dangerous for the fetus. Well, when the girl returned and went to the doctor, it turned out that there was no pregnancy at all, and she was wasting her monastic lifestyle on vacation.
“I was just furious. I am thinking of suing the manufacturer of the tests to compensate me for the spoiled rest, ”said the vacationer.
Well, Professor Granovsky once again emphasizes: the best way to confirm pregnancy is a blood test. Therefore, if you suspect that the test is deceiving you, do not dilute the urine with water and try again (yes, they say that such a “trick” sometimes helps). It is better to go to the doctor right away and dispel all doubts.