Strips of Hope: Accuracy of Home Pregnancy Tests and New Developments

Abstract

The first home pregnancy test was introduced in 1976. Since then, pregnancy tests have become the most common diagnostic assay used at home. Pregnancy tests use antibodies to detect human chorionic gonadotropin (hCG). It is an ideal marker of pregnancy since it rises rapidly and consistently in early pregnancy and can be detected in urine. The most advanced home pregnancy test currently available assesses the level of hCG found in urine and claims to provide women with reliable results within just a few weeks of pregnancy. Today, over 15 different types of home pregnancy test are available to buy over the counter in Germany. Many tests claim to be highly accurate and capable of detecting pregnancy before the next monthly period is due, although claims such as 8 days prior to menstruation are unrealistic. However, users and healthcare professionals should be aware that, although all are labelled as CE, there are currently no standard criteria for testing performance and claims. This review provides an overview of the development of home pregnancy tests and the data on their efficacy together with an analysis of published data on the accuracy of hCG for the detection of early pregnancy and studies on the use of home-based pregnancy tests. Preliminary data on some home pregnancy tests available in Germany are presented which indicate that many results do not match the claims made in the package insert. Healthcare professionals and women should be aware that some of the claims made for home pregnancy tests are inconsistent and that common definitions and testing criteria are urgently needed.

Keywords: hCG; pregnancy; pregnancy test.

Fig. 1

Daily increase in urinary hCG in early pregnancy in three different studies: The UK Early Pregnancy Study , the UK Standard Care Ultrasound Study and the US Gestational Age Study . The grey area is the 10th to 90th centile band for the US Gestational Age Study .

Fig. 2

Impact of reference method used to determine pregnancy duration (day of pregnancy calculated from LMP (− 14 days) or from ovulation (LH surge + 1 day) on variability of urinary hCG in early pregnancy normograms by day. Median hCG levels overlay by day; variability was markedly increased when pregnancy duration was calculated from LMP as opposed to ovulation. The grey area is the 10th to 90th centile band for the US Gestational Age Study .

Fig. 3 a

to c Relationship between duration of pregnancy assessed using the Clearblue Digital Pregnancy Test with Conception Indicator and a ultrasound and b LMP; c shows the relationship between pregnancy duration assessed by ultrasound and LMP [27]. CAPT: Clearblue Advanced Pregnancy Test with Conception/Weeks Indicator; CRL: crown rump length; LMP: last menstrual period. A Bland-Altman plot of differences is a method to analyse agreement between two different, but highly correlated methods of measurement. The plot investigates the existence of any systematic difference between the clinical measurements. If the mean difference ± 1.96 SE (standard error, dotted line) of the two methods contains zero then the two methods can be used interchangeably.