Women’s health
By the early 1900s, most large hospitals had a central laboratory facility dedicated to diagnostic testing staffed by clinical chemists.5 At this time, the discovery of the hormones associated with pregnancy gave clinicians a means for testing for them, in ways not unsimilar to the clinicians of the past, using urine. The age of modern point-of-care pregnancy testing was predicated on the fact that a woman’s body produces a hormone called human chorionic gonadotropin (hCG) after an egg is fertilised, and that these hormones are present in urine.6 In 1927, the first iterations of urine hCG
pregnancy tests were developed, with animals effectively becoming bioassays. A woman’s urine was injected into an immature rat or mouse. If the rodent had a resulting oestrous reaction, in simple terms went into heat, it implied the presence of the hCG hormone in the woman’s urine, confirming pregnancy. By the 1930s, in addition to rodents, rabbits,
frogs, and toads became the unfortunate subjects of bioassay testing to determine whether ovulation could be induced.7
In addition
to observing whether the animals went into heat, the animals were killed so that their ovaries could be examined. The tests became commonly known as “rabbit tests”. However, they were expensive, time-consuming and not always accurate, notwithstanding the testing resulted in the untimely death of the animal. Thankfully, throughout the 1950s and 1960s
the science of pregnancy testing progressed beyond the use of animals, and bioassays were replaced by immunoassays using antibodies to test for the presence of hCG. The late 1970s saw the early-stage development of what we now know today as a lateral flow or lateral flow immunochromatographic pregnancy test, and while initial use was designed for use in a clinical setting, these tests were quickly developed for use at home. Lateral flow pregnancy testing works by collecting a sample of urine, from a urine stream or in a container. The “reaction zone” is coated with antibodies
that react to the presence of hCG hormones in urine, indicating a colour change and a “positive” reading. If no hCG is detected in the sample, there is no reaction and no colour change, thus rendering a “negative” test result. First generation tests had accuracy issues, and the percentage of false negatives was as high as 20 percent. Over the last two decades, lateral flow technology has been improved in pregnancy testing, with a 99 percent accuracy rate, as sensitivity has improved with results being delivered in a matter of minutes. This lateral flow technology has been
extended for diagnostic testing across a wide variety of conditions and illnesses using the same principle developed in pregnancy testing. The advent of COVID-19 in 2020 has meant the world has become very familiar with lateral flow diagnostics.
In women’s health specifically, lateral flow immunochromatographic testing has been used widely in applications beyond pregnancy for some time including the detection of ovulation and in detecting sexually transmitted diseases including HIV and syphilis. Maternity settings have also been the
beneficiary of the developments in lateral flow diagnostics particularly where time is of the essence and there is no opportunity to wait for laboratory-run tests, particularly in cases of premature rupture of membranes (PROM) and preterm labour (PTL).
PROM Premature Rupture of Membrane (PROM) remains one of the most controversial issues in obstetrics.8
has ruptured membranes before 37+0 weeks of pregnancy but is not in established labour. Pre- labour rupture of membranes (PROM) occurs in 8% of pregnancies and around 60% of these women will begin labour spontaneously within 24 hours.9
False positive PROM diagnosis may lead
to unnecessary interventions including delivery before term, or administration of prophylactic antibiotics, tocolytic agents and corticosteroids and where a false negative diagnosis may lead to less maternal and foetal observations or surveillance. Both scenarios can have adverse, sometimes fatal perinatal outcomes. Again, diagnostic testing for PROM has been
on an evolutionary journey as clinicians sought to augment their clinical observations with diagnostic testing. Developed in the 1950s the fern test was the first diagnostic test to be used to determine whether rupture of amniotic membranes had occurred. The test is done by collection of fluid from the vagina which is then allowed to dry for 10 minutes on a slide.10
The
cervical mucus forms fern-like patterns due to crystallisation of sodium chloride on mucus fibres. This pattern is known as arborization or ‘ferning’. The 1960s saw the use of nitrizine paper for the diagnosis of PROM. Amniotic fluid typically has a pH of 7.1–7.3, while normal vaginal secretions have a pH of 4.5–6.0. pH testing can be done by use of nitrazine strips which tur dark blue from yellow in fluids with pH above 6.5;1
but because of false positive results from The ability to determine whether
rupture of amniotic membranes has occurred is important as it has significant implications in the management of obstetric patients. A woman is described as having PROM if she
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interfering substances, including vaginal infections, blood, and semen, alternative sources of diagnostic testing were developed. The most recent National Institute of Clinical Excellence (NICE) Guidance on Preterm Labour and Birth (NG25) advocates the use of two biomarkers in identifying premature rupture of membranes, namely insulin-like growth factor
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