pregnancy test
A pregnancy test is used to prove pregnancy . To subscribe to pregnancy sign to ensure that actually are pregnant, when is immunological pregnancy test, the presence of pregnancy-maintaining often hormone hCG tested in the body. This hormone is found in trophoblastic tissue , which is made by the fetus or placenta , so it can only be detected during pregnancy.
From the sixth week of pregnancy, an embryo can also be detected by means of an ultrasound examination .
Urine test
The home urine test or quick test with a stick is the most commonly used method to prove pregnancy. All of these tests are based on a 1980 Unipath Ltd. principle patented in Great Britain. The stick tests are available in pharmacies, drugstores and in some cases also in department stores and by mail order.
The test using the test strip / stick held in the urine stream leads to a result with a reliability of over 95 percent no earlier than approx. 14 days after fertilization of the egg cell . Since morning urine contains higher concentrations of hCG, pregnancy can be detected better and earlier. In order to provide even more reliable proof of pregnancy, a further test (another urine test, blood draw or ultrasound examination) can then be carried out by a doctor or midwife.
In medical laboratories, the quantitative hCG concentration can also be measured in the urine. This is given in international units (IU) per liter. Initially, the values double every 2.5 days until they level off around 45,000 IU / l from the 8th to 10th week of pregnancy. This can also be used to answer forensic medical questions, for example whether there was an abortion .
If pregnancy is expected and the urine test is negative, it is possible that not enough hCG has been produced, which is why the test should be repeated later or a blood test carried out.
How the rapid test works
The rapid test is an immunochromatographic test based on the principle of the lateral flow test . If the test strip is moistened with urine, the hCG antigen contained in the urine (green) binds to a dye-labeled hCG antibody contained in the test strip (pink). The antigen-antibody-dye complex (green and pink) migrates to the test zone, in which a second hCG antibody (light gray) is fixed. This immobilized antibody (light gray) binds the migrating antigen-antibody-dye complex (green and pink) in this zone and stains it. Excess dye-labeled hCG antibody (pink) migrates to the control zone, in which an anti-Fc antibody (dark gray) is fixed. This immobilized anti-Fc antibody (dark gray) binds the excess dye-labeled hCG antibody (pink) in this zone and also stains it. The last process can only take place if enough liquid has got into the test strip to make the dye-labeled hCG antibodies (pink) sufficiently mobile. The control zone ensures that the result shown in the first strip is correct.
Digital tests
There are also tests that show the result as text on an LCD display. Since only a conventional test strip is read inside by means of photodiodes, these tests can only be used once and do not offer increased accuracy. According to a publication by the United States Department of Health, the additional evaluation procedure results in an increased percentage of “not pregnant” reports even though a pregnancy is present (false negative result).
reliability
Especially in the first five weeks of pregnancy, the hormone concentration in the urine can be below the detection limit of the urine test, so that the test result is false negative .
Blood test
By taking a blood sample, sufficient amounts of hCG can be found in the blood serum seven to ten days after fertilization . This in turn means that pregnancy can be proven before the presumably missed period.
Ultrasound examination
An ultrasound scan can determine pregnancy from around the sixth week of pregnancy. Usually only the implantation of the embryo in the uterus is visible (accumulation of tissue at a certain point). The fetus itself can only be seen later.
Historical test methods
As early as ancient Egypt, attempts were made to prove a possible pregnancy using urine samples. The urine of a possible pregnant woman was poured over cereal grains. If the grains sprout, it was considered an indication of pregnancy.
In the late Middle Ages, the early determination of pregnancy in cattle was described by means of uroscopy , taking into account color and texture as well as layering after the cow urine was stirred.
The first modern pregnancy test was the Aschheim-Zondek reaction developed in 1927 , a test that was carried out on mice. Until the 1960s, pregnancy tests were carried out with the help of African clawed frogs . This test is known as the frog test ("Galli-Mainini test"). The test subjects' urine was injected into the frogs . If it was a pregnant woman's urine, the frog began to spawn in response . The Glaser-Haempel fish test developed by Erhard Glaser and Oskar Haempel also made a pregnancy diagnosis ; In the process, when the urine of pregnant women was injected into the water, the spontaneous development of the laying tube was triggered in female bitterlings . This became obsolete after the test for chorionic gonadotropin in pregnant woman's urine.
False positive results
A false proof of pregnancy - ie a "pregnant" report even though there is no pregnancy - can be provided by chorionic cell carcinomas and other germ cell tumors , as these can also produce the hormone hCG. An incorrect development of the fruit system in the first few days after fertilization and implantation of the egg cell can also lead to a positive result, although the fruit has already passed (possibly noticeable as a delayed menstrual period ).
Web links
- Pregnancy tests on netdoktor.at
- Answer to the question: When does pregnancy test begin? on ab-wann-schwangerschaftstest.de
Individual evidence
- ↑ United States Department of Health and Human Services Publication ID 2183557203; 2011
- ↑ Gundolf Keil : 'Rinderharn-Traktat'. In: Author's Lexicon . Volume VIII, Col. 79 f.
- ↑ a b Axel M. Gressner: Lexicon of Medical Laboratory Diagnostics . Springer-Verlag, 2013, ISBN 978-3-642-12921-6 , p. 262 ( limited preview in Google book search).
