Implementation of placental growth factor (PlGF)-based testing to aid diagnosis of suspected pre-eclampsia at Lancashire Teaching Hospitals NHS Foundation Trust

Our aims were to:

• To improve the patient pathway for mothers and babies at LTH.
• Ensure that the right patients were in hospital and the right patients were sent home.
• Improve the diagnosis of pre-eclampsia.
• Even though there is a cost implication to introducing the sFlt-1/PlGF ratio test this would hopefully enable improvements to the pathway to be made which could reduce costs. This includes improved mother and baby outcomes.

Pre-eclampsia is a multisystem hypertensive disorder of pregnancy that affects approximately 3 to 5% of all pregnancies. If a timely diagnosis is not made pre-eclampsia can be associated with significant maternal and foetal morbidity and mortality. 

Women can often be asymptomatic which can complicate its diagnosis.  Traditionally, the diagnosis of pre-eclampsia has relied upon the use of clinical features and non-specific biochemical markers which have inherent errors.

Lancashire Teaching Hospitals (LTH) comprises two hospital sites, one large teaching hospital site (Royal Preston Hospital) and a smaller district general hospital site (Chorley District Hospital).  It provides maternity services covering approximately >4500 births per year, with a midwife-only lead service at the Chorley site.

Lancashire Teaching Hospitals (LTH) Biochemistry Department worked closely with the Obstetrics team to implement the Roche Elecsys sFlt-1/PlGF ratio markers into routine practice. The service is 24/7 random access, UKAS accredited. UKAS is the National Accreditation Body for the United Kingdom.

This included Clinical Biochemists and Biomedical Scientists on the Biochemistry side being in regular communication with Obstetric consultants and midwives. This was done through regular and ad-hoc meetings and built into pre-existing governance meetings. Additionally, support was also required from IT to ensure seamless integration of the test.

The department provides the service to antenatal clinic, maternity wards and obstetrics triage teams across both sites. However due to the high-risk nature of pre-eclampsia the likelihood is the majority of tests would be done for the teaching hospital location. The sFlt-1/PlGF ratio analysis was performed on the Roche Elecsys e801 analyser at the Preston site. The service implemented by Biochemistry was available 24/7, random access and UKAS accredited.  A four-hour turnaround time is offered to enable clinical decisions to be made while the patient is on the hospital site.

For entry into the developed pathway a patient was identified as per NICE guideline DG23. At this point the midwife would bleep the biomedical scientist in the biochemistry laboratory to inform them there was a sample coming for analysis. The patient would then be bled for the sFlt-1/PlGF ratio, along with other routine tests and the sample is sent in the air tube system for analysis.  Once the sample is received in the laboratory it is analysed and the result is made available on the hospital information system.  Additionally, the result is also phoned to the requesting midwife.  At this point a clinical decision can be made as to whether the patient is admitted or discharged. This service was implemented in February 2019 and provides about 40 tests per month.

Furthermore, a hub and spoke model was also instigated with Blackpool Teaching Hospitals where the sFlt-1/PlGF ratio test was utilised in a slightly different model.

With this pathway the patient is identified as per NICE guideline DG23 as requiring a sFlt-1/PlGF ratio test and the clinical decision to admit or discharge is made before the clinician gets the results back. The sample is transported to the hub laboratory at Royal Preston Hospital for analysis on routine daily transport and analysis is carried out with a 4-hour turnaround time. The patient result is sent back using the National Pathology Exchange (NPEx) IT system where the results are available on Blackpool’s IT systems as soon as they are released from LTH.  At this point the sFlt-1/PlGF ratio can then be used to make a further clinical decision for that patient.

We have been running the test successfully at LTH for almost two years and this is now embedded in routine care.  Midwives are taking routine bloods for these patients who present with hypertension in pregnancy and the addition of the sFlt-1/PlGF ratio to these requests does not add any additional workload.

From audit data, we have shown that the use of the test allowed 100% of mothers, without any other obstetric complications, with a result of <38 to be discharged home safely.  Additionally, the test provides reassurance for mothers since a result of <38 rules out pre-eclampsia for one week.

We have found the use of the sFlt-1/PlGF ratio test useful in diagnosis of pre-eclampsia and this is particularly useful when risk stratifying which patients to keep as in-patients.

We have identified overuse in mothers who don’t qualify for the test according to NICE DG23.  In order to address this we have updated our algorithms to make it clearer when to request the test and have displayed these in prominent locations.

• Work closely with all stakeholders: clinical scientists, BMS, obstetricians, midwifes, pathology reception staff, IT.
• Consider the whole patient journey/pathway.
• One pathway doesn’t suit all however PlGF testing can be integrated.
• Clarity was required on the indication of use.