Pregnancy tests. can we trust them?
Suhr, P.
Ugeskrift for Laeger 145(27): 2104-2106
1983
ISSN/ISBN: 0041-5782 PMID: 6612843 Document Number: 202618
The reliability of pregnancy tests, which detect the elevated level of chorionic gonadotropin (CG) in the urine of pregnant women, as well as the implications of positive and negative results, faulty readings, manufacturers' research guidelines, and public awareness are discussed. False positive results occur in 5/1000 tests and can result from (CG) being present in hydatidiform mole and choriocarcinoma; follicle-stimulating hormone (FSH) or luteinizing hormone (LH) can also trigger positive results. False negative readings can occur as a result of the low level of CG early in pregnancy, or from failure to test morning urine, which has the highest concentration of the hormone. A nomograph showing the number of false negative reactions as a function of phases of gestation takes into account the capacity of the test (100, 500, 1000 IE CG per liter urine), and can assure a much higher rate of accuracy. Another cause of false readings can be the presence of soap traces in the test tube -- this can be eliminated by the use of the slide test spiller. In 1982, about 355,000 tests were sold to the public, pharmacies, laboratories, and doctors. Public education by pharmacies can help assure a 95% reliability rate, especially if 1-2 weeks after the 1st test is taken, a 2nd one is done. These tests are reliable if taken at the right time, but only consultation with a doctor can assure certainty about pregnancy.