PLGF Testing to diagnose suspected preterm preeclampsia

Hypertensive disorders of pregnancy affect 10-15% of the pregnant population. Pre-eclampsia affects 2.8% of women and birthing people, with 25% of cases in singleton pregnancies developing before 37 weeks gestation (Hurrell et al, 2024). Perinatal outcomes are poorest in this group, in part due to delay in accurate diagnosis.

Placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) are biochemical markers found in maternal plasma serum that can measure the health of the placenta and can be used to diagnose suspected pre-eclampsia. sFlt-1/PlGF ratio testing offers a high diagnostic accuracy for predicting pre-eclampsia needing delivery and is now recommended by NICE (2023).

PlGF testing should be used to rule-out pre-eclampsia in women presenting with suspected pre-eclampsia between 20+0 and 36+6 weeks. The aim of the testing is to reduce over-diagnosis and unnecessary preterm delivery to optimise perinatal outcomes for mother and baby. Women presenting with new onset hypertension and significant proteinuria should be managed as having a diagnosis of pre-eclampsia, and PlGF testing not offered.

All women attending with suspected pre-eclampsia should have the following initial tests performed/sent to lab:

• Blood samples: FBC, LFTs, U&Es
• Urinalysis: Dipstick midstream urine sample
• Urine samples: Lab-verified urine PCR (protein: creatinine ratio) or ACR (albumin: creatinine ratio)

These tests should inform decision making on whether to offer sFlt-1/PlGF testing, using the below criteria. Lab-verified urine PCR or ACR values should be used when aiding diagnosis. If not available within 3 hours of sending, dipstick analysis values can be used.

Women at 20+0 to 36+6 weeks gestation, presenting with one of the following:

• New hypertension (>140/90mmHg) requiring treatment with slight proteinuria (PCR <30mg/mmol or ACR <8mg/mmol or ≤1+ on urinalysis)
• Normal BP with new onset significant proteinuria (PCR >30mg/mmol or ACR >8mg/mmol or ≥2+ on urinalysis)
• Worsening essential hypertension
• Worsening proteinuria in pre-existing renal disease/diabetes
• Suspected placental insufficiency (USS suggestive of SGA <10^th centile or abnormal umbilical artery Doppler PI >95^th centile or oligohydramnios)

Women from 20+0 weeks presenting with hypertension (>140mmHg/90mmHg) and significant proteinuria (PCR >30mg/mmol or ACR >8mg/mmol or ≥2+ protein on urinalysis) should be managed as a confirmed diagnosis of pre-eclampsia and not offered sFlt-1/PlGF testing.

Taking the sample

Discuss with Obstetric Consultant about appropriateness of PlGF testing

• Collect 1x serum gel tube (brown tube) sample

All NHS Borders samples are processed at the lab at St John’s Hospital, Livingston. sFlt-1/PlGF ratio testing will be available 24hrs a day, 7 days a week.

Contact the biochemistry lab at SJH on telephone 01506 523160/1 to inform the lab before a sample is sent so the analyser can be set up: 

• Provide a contact number for results to be phoned back to.

To enable rapid transfer of the sample please arrange a taxi deliver to SJH.

Put the sample/biochemistry bag into a brown envelope to conceal patient-identifiable details and hand to taxi driver. The driver will need to walk it up to the labs at SJH on arrival.

NICE diagnostics guidance DG49. PlGF-based testing to help diagnose suspected preterm pre-eclampsia (NICE, 2022). https://www.nice.org.uk/guidance/dg49/chapter/2-The-diagnostic-tests

NICE guideline NG 133. Hypertension in pregnancy – diagnosis and management (NICE, 2023). https://www.nice.org.uk/guidance/ng133

Hurrell et al, 2024. Repeat placental growth factor-based testing in women with suspected preterm pre-eclampsia (PARROT-2): a multicentre, parallel-group, superiority, randomised controlled. Lancet 2024; 403: 619-631. https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(23)02357-7.pdf