LONDON – A home digital pregnancy test is able to correctly estimate the likely week of conception, according to the results of a 10-month, prospective observational study of 1,505 nonpregnant U.S. women.
"There was a high [98%] level of agreement between the digital pregnancy test and standardized ultrasound," Sarah Johnson, Ph.D., said in an interview at the annual meeting of the European Society of Human Reproduction and Embryology.
The results of the digital pregnancy test were compared with ultrasound measurements performed at approximately 12 weeks after the woman had her last menstrual period (LMP).
"We received clearance from the Food and Drug Administration last December, and all being well it should be on the shelves in September," said Dr. Johnson, who is a scientific and medical affairs manager for SPD Development of Bedford, England. The digital pregnancy test is already available in the United Kingdom* based on data from a previous study (Curr. Med. Res. Opin. 2011;27:393-401).
Dr. Johnson noted that this is the first home pregnancy test to provide an accurate and early assessment of pregnancy at the time when a woman first suspects that she might be pregnant. It is also the first test to provide a digital readout, which is potentially simpler for women to understand than seeing a line in a window to indicate whether they are pregnant or not.
Similar to other home pregnancy tests, the digital pregnancy test measures levels of human chorionic gonadotrophin (hCG) excreted in the urine. Measuring hCG is a tried-and-tested method of confirming pregnancy as the hormone plays a critical role in early pregnancy, helping with the implantation of the embryo and preventing further oocyte development.
Unlike existing tests, however, the digital pregnancy test estimates the time since conception based on thresholds of hCG, which have been shown to rise rapidly after ovulation has occurred, and measurement of this hormone in the urine reflects the duration of pregnancy (Curr. Med. Res. Opin. 2009;25:741-8).
In using the digital home pregnancy test, the woman can either hold the test strip in the urine stream for 5 seconds or dip it into a urine sample collected in a clean container for 20 seconds. Results from the test are then given in a few minutes as a digital readout saying if the woman is "pregnant" or "not pregnant," with additional numbers displayed if conception was likely to be 1-2, 2-3, or 3+ weeks ago.
During the study, women were required to provide urine samples every day throughout their menstrual cycles, a random sample of which were then tested in the laboratory using the digital home pregnancy test.
A total of 250 women became pregnant during the study, with sufficient data on 153 women available for analysis. All of these women had ultrasound performed at approximately 11-13 weeks of their pregnancy to determine the gestational age according to the crown rump length measurement. More than 3,600 digital pregnancy tests were preformed in three batches, with the technicians blinded to the samples.
One of the interesting observations of the study is the inaccuracy of the LMP, Dr. Johnson said. All the women in the study planned on becoming pregnant and were carefully monitoring their menstrual cycles. Although they thought they knew exactly when their LMP was, the urine assessments suggested they were wrong by about 5 days.
"When a woman thinks she is pregnant, all she has is her last menstrual period, and that in so many cases is wrong, so this new test provides something that can provide greater accuracy," Dr. Johnson suggested.
SPD Development also has a digital ovulation test that is soon to be released in both the United States and the United Kingdom.
"Normal ovulation tests just measure luteinizing hormone [LH], so they tell you the best 2 days [to conceive]," Dr. Johnson said. The digital ovulation test still measures the LH surge, which indicates ovulation has occurred, but it also measures levels of estrone-3-glucuronide (E3G), which is a major urinary metabolite of estradiol. Levels of E3G rise a couple of days before the LH surge.
"By measuring [E3G], you are actually telling a woman about those additional fertile days during which she can also get pregnant before the 2 peak days," Dr. Johnson explained. Data presented in a poster at the annual meeting of ESHRE showed that the new digital ovulation test identified 4 or more fertile days in 80% of menstrual cycles.
The digital ovulation test will come as a kit with replaceable test strips. A woman urinates on the test strip, puts it into the reader, and the device then remembers the result and helps the woman identify her most fertile period.