Elecsys^® sFlt-1/PIGF ratio aids laboratories, clinicians in predicting the risk of severe preeclampsia

The difference between an unnecessary preterm delivery and a life-threatening emergency can now be predicted with 79% accuracy, thanks to a new biomarker test that's transforming preeclampsia care. The Elecsys® sFlt-1/PIGF ratio, cleared by the U.S. Food and Drug Administration (FDA) in February 2025, offers a fast and reliable method for stratifying hospitalized patients into low- and high-risk categories for developing preeclampsia with severe features within two weeks of testing.

The ratio’s FDA clearance comes as cases of preeclampsia are on the rise. In the U.S. alone, the condition has increased by 25% over the past four decades,¹ affecting 1 in 7 hospital deliveries, or approximately 165,000 to 220,000 pregnancies each year.^2,3 Disproportionately affecting Black women, the condition is a leading cause of maternal and infant illness and death.^4,5

Preeclampsia is characterized by high blood pressure and signs of organ damage, most commonly to the kidneys and liver. Clinical presentation varies widely, making it difficult to diagnose and manage. Once preeclampsia is present, it can be challenging for clinicians to predict whether it will progress to a severity that could threaten the mother’s life or the life of her baby. In fact, the typical indicators of preeclampsia progression, including high blood pressure and protein in the urine, have a positive predictive value of just 18% to 20%.⁶ Currently, the only treatment for preeclampsia is preterm delivery of the fetus and removal of the placenta.

Early preeclampsia diagnosis and risk assessment are key

Recent studies have shown that identifying patients at high risk for developing severe preeclampsia can lead to better prediction, earlier interventions and reduced adverse outcomes.^7,8 As a prognostic tool to support clinical decision-making, the sFlt-1/PIGF ratio, available on widely accessible platforms like the cobas® integrated solution, is a significant step forward in the clinical management of a complex medical condition.

sFlt-1 and PIGF are key angiogenic biomarkers in the formation of blood vessels during pregnancy. An angiogenic imbalance has been proven to play a causal role in the development of preeclampsia. In fact, their concentrations in maternal serum are altered even before the onset of disease.⁹

Fast turnaround time changes the clinical care dynamic

With results available in under 18 minutes, the Elecsys sFlt-1/PIGF ratio provides fast results when clinicians and patients need them most. In the treatment of preeclampsia – a condition that can progress rapidly – the accelerated turnaround time has significant implications for clinical decision-making.

“Many of the urgently required deliveries for preeclampsia happen within a few days of presentation, and even when the mother is going to be managed expectantly with more frequent monitoring and enhanced surveillance, the care team must decide how to treat the mother well before the test results from a reference lab return,” Dr. Berg explained. “I would expect that having results available on the same day as the mother presents with symptoms would dramatically change the ratio’s utility and impact.”

Clinically validated results – PRAECIS study at Roche

The PRAECIS study at Roche was a population-based non-interventional study run on archived samples collected from 18 U.S. tertiary and community hospitals to validate the Elecsys® sFlt-1/PlGF ratio for predicting preeclampsia with severe features.⁷ The study enrolled pregnant women ≥18 years old admitted to the hospital between 23+0 and 34+6/7 gestational weeks with singleton pregnancies and hypertensive disorders of pregnancy. 

The primary outcome was the prediction of preeclampsia with severe features within two weeks of testing. The Elecsys sFlt-1/PlGF ratio outperformed the standard of care risk biomarkers that clinicians typically use to predict severity, supporting the sFlt-1/PlGF ratio as a complementary test to the existing standard of care. Standard of care risk biomarkers include systolic and diastolic blood pressure, alanine aminotransferase, aspartate aminotransferase, creatinine, and platelets.

A second study led by the University of Chicago Medical Center improved upon the PRAECIS results. The study, published in the American Journal of Obstetrics and Gynecology in July 2024, showed a positive predictive value of nearly 79% compared to the standard of care. Similar to the PRAECIS trial, the negative predictive value was very high at 94%.¹⁰ The trial, which reported real-world evidence for clinical utility after the implementation, revealed that the rate of preterm delivery was lower in pregnant women with a low sFlt1/PlGF ratio.

Factors influencing ratio use in clinical practice

In June 2024, the American College of Obstetricians and Gynecologists (ACOG) issued updated clinical practice guidance acknowledging the sFlt-1/PIGF ratio as an additional tool for use with other Recommended measures to predict the risk of developing severe preeclampsia.¹¹ In addition to the updated ACOG guidance, the availability of the FDA-cleared sFlt-1/PIGF ratio test on the Elecsys platform sets the stage for more widespread use and application of the ratio in the care and treatment of pregnant women with preeclampsia. Availability of the biomarker test in more hospital-based core laboratories in both urban areas and small communities will likely increase access to the predictive tool, helping to address socioeconomic and health disparities related to complications from pregnancy.

“Remember that all medical decisions made when women present with preeclampsia affect the health outcomes of both mother and child," said Dr. Berg. “Whether the result is high risk or low risk, this information may be beneficial to both patients. I foresee the sFlt-1/PIGF ratio becoming the standard of care for evaluation and decision-making for all women with a hypertensive disorder of pregnancy. Consequently, the widespread application and use of this predictive biomarker test will prevent the majority of cases that progress to severe disease with end-organ damage.”

Disclaimer
Key precautions for labs:
The ratio must be calculated using Elecsys sFlt‑1 and Elecsys PlGF results obtained on the same patient sample and the same cobas immunoassay analyzer. The assays are not intended to be used individually. Use of another manufacturer’s assays may result in significantly different ratios.

sFlt‑1 and PlGF values determined on patient samples using other manufacturers’ assays may result in significantly different ratios, which could lead to wrong diagnostic conclusions. Therefore, only the Elecsys sFlt‑1 and Elecsys PlGF assays should be used to calculate the Elecsys sFlt‑1/PIGF ratio.

References