How Reliable Are Home Pregnancy Tests?
Pregnancy tests have been used as far back as the 1970s, with EPT being the first home pregnancy test. Since then, manufacturers have created devices using different forms of technology.
Two types of devices are currently available on the market—manual and digital home pregnancy tests. Manual devices typically show a faint line, corresponding to a positive pregnancy test, whereas digital home pregnancy tests show a “yes” or “no or a “pregnant” or “not pregnant” sign on a small screen.
These pregnancy self-test kits rely on detecting human chorionic gonadotrophin (hCG), and manufacturers have claimed that their kits can detect extremely low levels of this hormone, as easily as during the first week after conception.
Less sensitive tests can detect the levels of hCG when these increase to higher levels in subsequent weeks after conception. So, to avoid getting a false negative, especially when you’ve been rooting for a baby, you need to know the device you’ll be buying and when it would be most appropriate to test.
At the time this is being written, the most helpful and recent study that examines the advantages and disadvantages of different pregnancy self-test kits is that conducted by Cole.
Cole investigated the abilities of six over-the-counter pregnancy tests to detect pregnancy in 120 urine samples in the days leading up to and following the time of a missed period. Clearblue Easy, EPT and First Response digital and manual devices were assessed in the study.
Pregnancy Detection Rate in the Third Week after the Last Period
All six pregnancy tests assessed by Cole appeared capable of detecting hCG in the third week (after the last period) of pregnancy.
First Response manual appeared to be the best device in detecting very small levels of pure hCG (sensitivity, < 3.3mIU/mL), followed by EPT manual and Clearblue Easy manual (sensitivity, 5.5–11 mIU/mL in each case). A similar result was observed with the digital devices of all three brands.
Pregnancy Detection Rate Three Days after a Missed Period
First Response manual and First Response Gold digital could detect pregnancy three days after a missed period at rates of 100% and 95%, respectively. EPT manual and EPT Certainty digital devices had detection rates of 80% (in both cases), whereas Clearblue manual and digital had detection rates of 75% (in both cases).
From these results, it appears that First Response pregnancy test is the winner in detecting early pregnancy.
Pregnancy Detection on the Day of Missed Period
First Response manual and digital devices yielded a high detection rate (97%) on the day of the missed period. Lower detection rates were documented with EPT manual and digital (54% and 67%, respectively) and Clearblue manual and digital pregnancy self-test kits (64% and 54%, respectively).
Pregnancy detection rate four days prior to the missed period
The First Response manual and digital tests had detection rates of 58% and 42%, respectively. Conversely, the detection rates were much lower for the EPT manual and digital tests (6.3%) as well as the Clearblue manual and digital tests (8.8% and 3.8%, respectively).
Overall, both the manual and digital pregnancy tests appeared not to be very beneficial in detecting pregnancy before the date of the missed period.
A previous study (a meta-analysis) by Bastian et al. showed that the effectiveness of home pregnancy test (HPT) kits was greatly affected by the way women used them, suggesting that some women do not understand HPT kit instructions.
Manual Versus Digital Home Pregnancy Test Kits
Both manual and digital devices had approximately the same sensitivity rates in the study conducted by Cole.
The difference lies in that the results may be difficult to interpret with manual devices, which typically display faint lines.
This may confuse some women who might not be able whether their results are positive or negative. Thus, digital devices offer a greater advantage in that they display a definitive result: “Yes” or “No” or “Positive” or “Negative”.
Are Manufacturers Misleading Women with Their Claims of 99% Accuracy?
Probably not. It seems the way some manufacturers calibrate their pregnancy test might have affected the results in the study by Cole.
The manufacturer of Clearblue, for example, uses the luteinizing hormone peak plus 17 days (four days longer than that considered in experiments) to calibrate their pregnancy self-test devices. On their website, the manufacturer reports that Clearblue pregnancy tests are over 99% accurate.
Moreover, there are concerns that women’s understanding of HPT kit instructions and their use of the test may affect the reliability of these tests.
For more about clinical trials of home pregnancy tests, you can visit the website of the US National Institutes of Health.
Overall, home pregnancy tests are useful, but care must be exercised when purchasing these test kits. Visit review sites and forums to read reviews that are based on users’ experiences to get a better picture of what you’ll be getting for your money.
Further, after testing negative a few days prior to your missed period, it would be prudent to test again on the day or one week after your missed period to avoid a false negative.
Cole LA. The utility of six over-the-counter (home) pregnancy tests. Clin Chem Lab Med. 2011 Aug;49(8):1317-22. doi: 10.1515/CCLM.2011.211.
Bastian LA, Nanda K, Hasselblad V, Simel DL. Diagnostic efficiency of home pregnancy test kits: a meta-analysis. Available from: http://www.crd.york.ac.uk/crdweb/ShowRecord.asp?LinkFrom=OAI&ID=11998001648. Accessed March 26, 2017.
Pregnancy Test – Clearblue Innovations Give You Added Benefit. Clearblue US Website. Available from http://www.clearblueeasy.com/pregnancy-test.php. Accessed on March 26, 2017.