This site is intended for health professionals only

Home pregnancy and fertility testing

Mark Jones
MSc BSc (Nurs) RN RHV
Director
Community Practitioners' and Health Visitors' Association
40 Bermondsey Street
London SE1 3UD
E:mark.jones@amicus-m.org
W:www.amicus-cphva.org.uk

The majority of practice nurses will at some time have met a patient who is either overjoyed or distraught at the news that they are a pregnant. This is an incredibly emotional time for women and their partners or friends, and today many take the step of checking either their stage of ovulation or the possibility of pregnancy using a commercially available kit at home, before requesting confirmation from the GP practice or other healthcare provider. But just how accurate are these kits, and how do they actually work? Furthermore, should practice nurses and other health professionals be advocating their use, and if so what advice needs to be given?

Home pregnancy testing
Mode of action

Our memory of past study of human biology will recall that once a fertilised embryo attaches to the uterine lining it needs to be stabilised and nourished. To this end, human chorionic gonadotrophin (hCG) is released by the rapidly developing placenta. hCG levels rise sharply after implantation and are detectable in the urine as soon as 24 hours after the event. It is the presence of hCG that home pregnancy tests are designed to detect. The user is required to either urinate directly onto a test strip or dip one into a pot of urine, and pregnancy is confirmed by way of a colour change in the test medium or the presence of a coloured line or lines, depending on the test selected.

Accuracy
Many home pregnancy tests claim an accuracy of 99%, and readily accessible sources of patient advice tend to confirm a figure approaching this: for example, the popular website "Babycentre" claims 97% accuracy when tests are used according to their instructions.(1) However, an often-quoted study by Bastian et al that looked at the home tests available in the USA (many of which are the same as those that can be bought in the UK) showed that at best a true detection rate of pregnancy was around 91% when volunteers tested previously collected samples of urine (range between 52% and 100%), and 75% when the subjects using the test were women who collected and tested their own samples (range 53-82%).(2) The study went on to conclude that for every one in four women who use the test and are pregnant, one will get a negative test result. It also suggested that for every four women who are not pregnant, one will have a positive test result.
These results may be attributed to test user error in addition to basic test inaccuracy, although other studies have questioned whether the aim of detecting the presence of hCG is adequate. For example, a study that questioned claims of "99% accuracy" determined that tests that simply sought to identify the presence of hCG could not be this accurate and that a test seeking to identify a variant of hCG - hyperglycosylated hCG (H-hCG) - would be far nearer the mark, especially on the first day of pregnancy.(3)

What to advise?
Clearly it is inappropriate to give a biochemistry lesson to the majority of would-be users of home pregnancy tests. Rather, advice needs to be given as to their correct use and the probability of their accuracy. By and large, patients should be encouraged not to rely on the result of a home test de facto, especially if they do not want to be pregnant. While many private- and charity-run clinics use home-type tests to verify pregnancy, a blood test is preferable. Blood testing uses the same hCG marker in providing a result but is far more accurate and a better option for those seeking to exclude pregnancy. As with all home tests for whatever condition (eg, cholesterol levels or influenza), the use of a pregnancy test in isolation at home removes the opportunity for consultation with a healthcare professional.
Obvious as it may sound, it is useful therefore to have literature available in the waiting area of the practice giving information sources for those who wish to discuss options around their potential pregnancy.
Practice nurses and other professionals who run health education groups should be ready to discuss the use of home pregnancy tests as a firstline indicator. Shew et al demonstrated that this is particularly relevant to those dealing with the school-age population.(4) Their study of 474 "sexually experienced youths" showed that 34% had used a home test and that almost half of those who obtained a negative result never followed up for confirmation with a healthcare provider. This group also reported less consistent use of contraception.
In summary, home pregnancy tests are widely used in the UK and are a popular private and discreet means of obtaining a result. Healthcare professionals should be familiar with the range available but be sure to advise potential users to be wary of claimed accuracy when this is based on a laboratory study rather than real-life analysis. Above all, patients should be advised to follow the enclosed instructions properly and seek confirmation of the result they obtained.

Home fertility testing
In contrast to the desire to determine pregnancy, many women wish to get pregnant on the one hand and avoid it on the other. In such cases the use of home fertility testing may be an option.
The most well-known home-use fertility test available in the UK is the "Persona" device marketed by Boots Chemists. Persona is a handheld device that takes readings of hormone levels in a woman and then produces a profile of her ovulation cycle. The varying chance of pregnancy is indicated by a traffic light system with a 15-day "red period" indicating the most likely time for pregnancy to occur with a claimed 94% accuracy.(5) Unfortunately, after its launch in 1996, Persona became the target of criticism from several women who became pregnant in the indicated "safe period". This resulted in a government warning that women should use the kit only if they did not mind getting pregnant.(6) A report by the Medical Devices Agency went on to say that Persona was essentially an electronic version of the rhythm method of contraception and that its 94% accuracy claim could not be substantiated, and that even if it were this would equate to 1 in 17 users becoming pregnant per year of use.(7) Boots stand by its figures, and each test kit includes a detailed guide indicating a range of situations that may jeopardise results and how to avoid them.
Other test devices based on similar urine dipstick procedures are available. They record times of "high" fertility by detecting when there are significant oestrone glucoronide levels present in the urine, and "peak" fertility time when a luteinising hormone (LH) surge occurs. Studies have shown that the ClearPlan fertility monitor (Unipath Diagnostics), which uses this method, is effective for couples planning a pregnancy as it shows the best time for sexual intercourse,(8) and is also a useful adjunct in artificial insemination treatment.(9) Simple urinary dipstick tests that rely on colour change on a test pad are also available. For example, using trained nurse testers and lay volunteers, Rudy and Estok found results from the OvuQuick test (Quidel) to be 93% accurate with 95% correlation in the testing groups,(10) and Miller and Soules' later study substantiated the accuracy.(11)
More intriguing is the suggestion that patterns of saliva can be used to identify ovulation and fertility, which is the theory behind the Calista Saliva Ovulation Test (Ecobrands).(12) As the concentration of oestrogen dissolved in saliva increases to the point of ovulation, samples of saliva smeared onto a glass slide and viewed through a range of commercially available "handbag-sized" microscopes show a characteristic "fern" pattern. While these kits are now widely available, researchers question whether it is possible to obtain a consistent sample in this way.(13)
The "Billings method" is based on the observation of cervical mucus. This has been found to be as accurate a predictor as ultrasonography in terms of diagnosis of ovulation, but skill and dedication are required to use this method.(13) Perhaps not a first- choice recommendation for the average patient!

Conclusion
Readily accessible test systems for use in the home are now commonplace, whether they be for pregnancy or fertility. Those for pregnancy are generally accurate enough as a firstline check, although follow-up confirmation by a healthcare provider is advisable. As for fertility tests, these are best used for the woman who is happy to become pregnant, rather than as a guide to prevention, unless personal choice or circumstances preclude the use of other forms of contraception.
These tests are mainly used away from the surgery, but practice nurses should have a reasonable working knowledge of those available and be able to explain their proper use, benefits and drawbacks.

References

  1. Babycentre. Home pregnancy tests. 2003. Available from  URL:http://www.babycentre.co.uk/refcap/2029.html
  2. Bastian LA, Nanda K, Hasselblad V, Simel DL. Diagnostic efficacy of home pregnancy test kits. A meta-analysis. Arch Fam Med 1998;7:465-9.
  3. Butler SA, Khanlian SA, Cole LA. Detection of early pregnancy forms of human chorionic gonadotrophin by home pregnancy test devices. Clin Chem 2001;47:2131-6.
  4. Shew ML, Hellerstedt WL, Sieving RE, Smith AE, Fee RM. Prevalence of home pregnancy testing among adolescents. Am J Public Health 2000;90:974-6.
  5. Boots. Persona starter pack. Boots online shop; 2003. Available from URL: http://www.boots.com/shop/product_details.jsp?productid=1010329
  6. BBC. Persona non grata. BBC Online; 3 July 1998. Available from URL:http://news.bbc.co.uk/1/hi/health/125944.stm
  7. Medical Devices Agency. Persona contraceptive device. London: MDA; 1998.
  8. May K. Home monitoring with the ClearPlan Easy fertility Monitor for fertility awareness. J Int Med Res 2001;29 Supp 1:14A-20A.
  9. Anthony FW, Gilbert D, Mason GM. Assessment of Clearplan fertility monitor for monitoring donor insemination patients with and without clomiphene treatment. Fertil Steril 2001;76(3):S185.
  10. Rudy EB, Estok P. Professional and lay interrater reliability of urinary luteinizing hormone surges measured by OvuQuick test. Obstet Gynecol Neonatal Nurs 1992;21:407-8.
  11. Miller PB, Soules MR. The usefulness of a urinary LH kit for ovulation prediction during menstrual cycles of normal women. Obstet Gynecol 1996;87:13-17.
  12. Guida M, Barbato M, Bruno P, Lauro G, Lampariello C. Salivary ferning and the menstrual cycle in women. Clin Exp Obstet Gynecol 1992;20:48-54.
  13. Guida M, Tommaselli GA, Palomba S, et al. Efficacy of methods for determining ovulation in a natural family planning program. Fertil Steril 1999;72:900-3.

Resources
Margaret Pyke Family Planning Centre
Information on home pregnancy and fertility testing
W:www.margaretpyke.org

Global Health Options
International database on sexual health and pregnancy and fertility tests available
W:http://g-h-o. co.uk/

British In Vitro Diagnostics Association
Industry association representing manufacturers of home testing kits.
W:www.bivda.co.uk