Increasing the availability of a simple blood test to diagnose pre-eclampsia

Pre-eclampsia is suspected in around 10% of UK pregnancies, affecting around 80,000 women each year. Early signs are high blood pressure and protein in the urine. If untreated, it can cause serious complications, putting both pregnant women and their babies at risk. In collaboration with Kings College London, University of Manchester researchers demonstrated that a simple blood test allows earlier and more accurate diagnosis.

High blood pressure and protein in the urine are used to make a diagnosis of pre-eclampsia. These observations vary a lot day to day, which sometimes makes it difficult for clinicians to be certain of the diagnosis. In women who already have hypertension (high blood pressure) and or chronic kidney disease, it is often not possible to use these signs to make an accurate diagnosis.

Placental growth factor (PlGF) is a hormone produced by the placenta during pregnancy. Women with pre-eclampsia have lower levels of PlGF. It can be detected in a simple blood test as a way to rule out or diagnose pre-eclampsia quicker and more accurately than by clinical diagnosis.

Professor Jenny Myers

Jenny is Clinical Professor at Manchester Maternal & Fetal Health Research Centre and Consultant Obstetrician at St Mary's Hospital.

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@jennymyers

In 2011-2012, the PELICAN study, led by King’s College London and co-authored by Professor Jenny Myers, was the first in the UK to look at PlGF biomarkers. Our research demonstrated that the PlGF test had a high sensitivity and a very good negative predictive value.

Although we knew that PlGF was an accurate way to detect pre-eclampsia, further research was needed to see if using this test would lead to improved outcomes for women and their babies.

The PARROT study ran in 11 UK maternal units and involved over 1,000 patients. It confirmed PlGF testing led to an earlier and more accurate diagnosis. In the group of women in the study who had the test included in their management, there was a lower rate of serious maternal complications.

The study indicated that by identifying those women at highest risk of complications and providing increased monitoring and earlier delivery of the baby where appropriate, it is likely that serious complications can be avoided.

Overall, implementation of the test did not increase the number of preterm births; this is likely to reflect the avoidance of premature births in those women where the diagnosis was more confidently excluded by use of the test.

The impact

Quicker diagnosis

Using the PlGF-based test in conjunction with standard clinical assessment reduces the average time for diagnosis of pre-eclampsia from four days to around two.

Earlier diagnosis reduces the risk of serious complications and allows women who are at high risk to be monitored more closely.

A negative test result also means that women can return to their usual antenatal care without needing additional hospital visits. 

NICE recommended

Based on the PELICAN study, the National Institute for Care Excellence (NICE) diagnostic assessment panel recommended use of PlGF tests to rule-out suspected pre-eclampsia in women between 20-34 weeks pregnant in May 2016. Professor Jenny Myers was a member of the NICE assessment committee.

In June 2019, NICE introduced new guidelines on hypertension in pregnancy: diagnosis and management. These guidelines also recommended PlGF testing.

Dr Kate Duhig

Kate is NIHR Clinical Lecturer at The University of Manchester.

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In July 2022, NICE diagnostic guidance was updated. While NICE previously recommended the test only to rule out pre-eclampsia, based on the PARROT study and other recent evidence, the panel recommended use of the test to both rule in and rule out pre-eclampsia.

Jeanette Kusel, acting director for medtech and digital at NICE, said: "These tests represent a step-change in the management and treatment of pre-eclampsia." She went on to say they are "extremely valuable to doctors and expectant mothers, as now they can have increased confidence in their treatment plans and preparing for a safe birth".

Potential NHS savings

Economic analysis of the PARROT trial showed that using the PlGF test saved the NHS £149 per patient tested, when accounting for the cost of the test at £70.

This is because early, more accurate diagnosis or rule-out of pre-eclampsia reduced the number of outpatient attendances and scans and in patient stays needed. This represented a potential cost saving of more than £2.5 million annually across NHS England.

Rolled out by NHS

In April 2019, Professor Tony Young, national clinical lead for Innovation at NHS England, confirmed that "the NHS, with partners in government, will be making this test more widely available across the NHS".

He said: "This innovative blood test, as set out in this new study, helps determine the risks of preeclampsia in pregnancy, enabling women to be directed to appropriate care or reduce unnecessary worry more quickly."

In 2020-21, PlGF tests were included in the NHS England Innovation and Technology Payments programme, which helps the NHS to adopt new innovations nationally.

Ongoing impact and other work

The PARROT 2 trial is now underway to see if repeat PlGF testing would have any impact on severe maternal and perinatal complications such as the need for neonatal admission or stillbirth and whether repeat testing would be cost effective.

Our collaboration with Lucy Chappell and colleagues from Kings College London is continuing. The NHS currently uses two main medications to control blood pressure in pregnancy. The Giant PANDA study is underway to determine which of these is the most effective and has fewest side effects for pregnant women.

The related Baby PANDA trial aims to compare how well these blood pressure medicines are used to treat high blood pressure in pregnancy work over a short time frame (12-24 hours).