Placental Growth Factor as a Triage Test: Weighing the Clinical Evidence

A new analysis published in npj Women’s Health examines one of the most consequential questions in modern maternity care: whether a single blood measurement of placental growth factor, a protein produced by the placenta, can reliably help clinicians decide which women with suspected preeclampsia need urgent attention and which can be safely monitored as outpatients. The study, authored by researchers affiliated with the Nature Research portfolio and published open access under the DOI 10.1038/s44294-026-00145-8, arrives at a moment when health systems worldwide are under pressure to improve outcomes in pregnancy while simultaneously containing costs, reducing unnecessary admissions, and avoiding interventions that carry their own risks.

Preeclampsia remains one of the leading causes of maternal and perinatal morbidity and mortality globally. The condition, which typically arises after the twentieth week of gestation, is characterized by new-onset hypertension and, in many cases, proteinuria, and it can progress rapidly toward seizures, stroke, hepatic and renal failure, placental abruption, and fetal growth restriction. The clinical difficulty is that its early presentation is notoriously nonspecific. Headache, edema, elevated blood pressure, and abnormal laboratory results overlap substantially with ordinary pregnancy discomforts and with unrelated disorders, which means that large numbers of women are evaluated, admitted, and observed for a disease that only a minority of them actually have or will develop.

This diagnostic uncertainty is precisely where placental growth factor enters the picture. PlGF is an angiogenic protein, a member of the vascular endothelial growth factor family, that plays a central role in placental development. In normal pregnancies, circulating levels of PlGF rise through the second trimester and peak in the third. In pregnancies complicated by placental dysfunction, the biological substrate of most early-onset preeclampsia, PlGF production falls measurably, sometimes weeks before the syndrome becomes clinically manifest. The inverse relationship between low PlGF and imminent preeclampsia has been replicated across numerous cohort and case-control studies, and commercial immunoassays measuring the protein have been developed and, in some jurisdictions, approved for clinical use.

The promise of a PlGF-based triage test lies in its negative predictive value. When a woman presents with suspected preeclampsia, a PlGF concentration above a predefined threshold substantially lowers the probability that she will require delivery within the following one to two weeks. Several health technology assessments, including guidance issued by national bodies such as NICE in the United Kingdom, have acknowledged this property, and PlGF-based tests have been recommended to help rule out preeclampsia in women presenting with suspicion of the disease between twenty and roughly forty weeks of gestation. The tests are not stand-alone diagnostic tools; results must always be interpreted alongside blood pressure, symptoms, and laboratory findings. But as a rule-out instrument, they have demonstrated an ability to redirect low-risk women away from hospital admission and toward community-based monitoring.

What the new analysis in npj Women’s Health sets out to interrogate is the distance between demonstration and deployment. Demonstrating that a biomarker correlates with disease is one thing; proving that measuring it changes decisions, decisions change outcomes, and outcomes improve enough to justify the cost and workflow disruption is quite another. This chain of evidence, sometimes called the analytic-validation-clinical validation-clinical utility framework, is the standard against which any proposed triage test must be judged, and each link in the chain has historically been weaker than the one before it for PlGF.

The clinical utility link deserves particular scrutiny. Randomized controlled trials evaluating PlGF-guided management have generally shown that knowledge of the biomarker result can reduce the time to preeclampsia diagnosis in women who ultimately develop the disease and can shorten hospital stays for those who do not. Whether these intermediate benefits translate into fewer adverse maternal or neonatal events is far less clear. Major adverse perinatal outcomes are comparatively rare in the populations enrolled in such trials, and trials powered to detect reductions in hard endpoints such as eclampsia, maternal death, or perinatal death would need to be very large, very expensive, and logistically demanding. In their absence, evidence of utility rests largely on surrogate outcomes and decision-modeling studies.

Cost-effectiveness modeling has nonetheless been broadly favorable. Because the alternative to biomarker triage is often prolonged inpatient observation of large numbers of women who never develop the disease, even a modestly accurate rule-out test can free up bed capacity, reduce staffing burden, and lower direct costs per episode of suspected preeclampsia. Health economic analyses in several national contexts have concluded that PlGF-based triage is likely to be cost-saving or at least highly cost-effective when used within structured pathways that specify exactly how clinicians should act on low, intermediate, and high results. The critical phrase is structured pathways: a biomarker result that arrives without an agreed management algorithm attached risks becoming an unused number, or worse, a source of unwarranted reassurance.

The analysis also engages with the limits of the technology that clinicians and laboratory directors must keep in view. PlGF performs best as a rule-out test for early-onset, placenta-driven disease. Its utility in late-term and term presentations is weaker, because preeclampsia at term frequently arises through mechanisms that are less tightly coupled to angiogenic imbalance. Assays from different manufacturers are not interchangeable, with differing thresholds and units, and results can be influenced by gestational age, multiple pregnancy, fetal sex, chronic hypertension, and intercurrent illness. Point-of-care and laboratory-based platforms also differ in turnaround time, which matters when the triage question is whether a woman can go home tonight or needs to be admitted for observation and possible delivery within days.

There are further implementation questions that any health system adopting PlGF triage must answer before the test can deliver on its potential. Who is eligible for testing, and at what gestational age? How quickly must the result be available for it to influence the same-day decision? What happens to women with intermediate values, which account for a meaningful fraction of tested patients and for whom the evidence is thinnest? How should repeated testing be used, given that serial PlGF measurements can add prognostic information but also generate anxiety and uncertainty when trajectories hover near thresholds? And how should clinicians communicate a favorable result to a woman without leaving her dismissive of genuine symptoms that the test cannot exclude?

Equity considerations compound these operational ones. The burden of preeclampsia falls disproportionately on women in low- and middle-income countries and on marginalized populations within high-income countries, precisely the settings where laboratory infrastructure, trained staffing, and follow-up capacity may be weakest. A triage strategy that works in a well-resourced maternity unit with round-the-clock laboratory support may fail, or even widen disparities, if deployed without the surrounding systems that make an outpatient monitoring pathway safe. Conversely, if low-cost point-of-care PlGF assays can be validated and integrated into referral networks, the same technology could improve risk stratification where it is needed most.

On balance, the evidence assembled across this literature supports a measured but genuine role for placental growth factor as a triage test in suspected preeclampsia. Its strength is not in diagnosing the disease but in identifying the substantial majority of evaluated women who can be safely managed without admission, thereby concentrating specialist attention on those at highest risk. Its weaknesses, including limited performance at term, unresolved questions about hard clinical endpoints, and demanding implementation prerequisites, are real but addressable through standardized pathways, assay harmonization, and continued prospective evaluation. As the npj Women’s Health analysis makes plain, the question facing maternity services is no longer whether PlGF carries clinically meaningful information, but how to embed it responsibly in the daily triage of pregnancy, where the test’s true value will be decided by the systems built around it.

Subject of Research: Use of placental growth factor blood testing to triage women with suspected preeclampsia in maternity care.

Article Title: Analyzing the clinical utility of placental growth factor as a triage test

Article References: Neff, N. L., Chen, H.-Y., Sibai, B. M., & Parchem, J. G. (2026). Analyzing the clinical utility of placental growth factor as a triage test. npj Women's Health. https://doi.org/10.1038/s44294-026-00145-8

Image Credits: AI Generated

DOI: 10.1038/s44294-026-00145-8

Keywords: placental growth factor, preeclampsia, triage test, biomarker, pregnancy, maternal health, angiogenic factors, diagnostics, prenatal care, clinical utility, health economics, obstetrics