Cost effectiveness of the sFlt1/PlGF ratio test as an adjunct to the current practice of evaluating suspected preeclampsia in the United States

Update on Preeclampsia and Hypertensive Disorders of Pregnancy

There have been recent advances in the prevention, diagnosis, and management of hypertensive disorders of pregnancy which complicate approximately 16% of pregnancies in the United States. Initiation of low-dose aspirin by 16 weeks' gestation reduces preeclampsia in high-risk women. The Food and Drug Administration approved the use of the soluble fms-like tyrosine kinase 1/placental growth factor ratio for the short-term prediction of preeclampsia. Pregnancy outcomes are improved in women with chronic hypertension when antihypertensives are initiated at a threshold blood pressure of 140/90 mm Hg. Women with prior preeclampsia have increased cardiovascular disease risk and should receive risk reduction counseling.

sFlt1/PlGF among patients with suspected preeclampsia when considering hypertensive status

BACKGROUND

In high-resource settings, biomarkers of angiogenic balance, such as the soluble fms-like tyrosine kinase-1 (sFlt1)/placental growth factor (PlGF) ratio, have been studied extensively to aid in evaluation of patients with suspected preeclampsia (PE), and have been incorporated into the 2021 International Society for the Study of Hypertension in Pregnancy definition of PE. The utility in under-resourced settings has not been as well characterized.

OBJECTIVE

This analysis sought to identify the role of the sFlt1/PlGF ratio in the evaluation of patients with or without hypertension who are suspected of having PE without other diagnostic information.

STUDY DESIGN

This is a secondary analysis of a prior prospective study of patients who were presented with suspected PE at ≥20+0 weeks' gestation at a single academic tertiary care center. Patients were recruited in the parent study from July 2009 to June 2012. In the original study, clinicians were masked to biomarker results, and patients were followed by chart review. In this analysis, the performance of the sFlt1/PlGF ratio (≤38, >38, or >85) was assessed alone in identifying both hypertensive and non-hypertensive patients at risk of evolving into PE with severe features (PE-SF; American College of Obstetricians and Gynecologists' definition) within two weeks of the triage visit (PE-SF2). Hypertension was defined as a blood pressure (BP)≥140/90 mmHg.

RESULTS

There were 1043 patients included in the analysis; of whom, 579 (55.5%) and 464 (44.5%) presented with or without hypertension, respectively. In triage, 332 (75.4%) of hypertensive patients presented due to BP concerns, and the remainder were evaluated due to other features (new-onset headache, proteinuria, or edema). On triage evaluation, 66.8% of all patients had a normal sFlt1/PlGF ratio ≤38, and 17.0% had an elevated ratio >85. Among hypertensive patients, a sFlt1/PlGF ratio ≤38 was a good rule-out test for PE-SF2 (negative likelihood ratio [LR-] of 0.15), and a ratio >85 was a good rule-in test (positive likelihood ratio [LR+] of 5.75). Among normotensive patients, sFlt1/PlGF was useful as a rule-in test for ratio >38 (LR+ 5.13) and >85 (LR+ 12.80). Stratified by gestational age, sFlt1/PlGF continued to be a good rule in and good rule out test at <35 weeks among those with hypertension but did not have good test performance ≥35 weeks. sFlt1/PlGF had a good test performance as a rule in test for >85 regardless of gestational age. In triage, 4.3% (30/693) of patients with sFlt1/PlGF ratio <38 had concurrent laboratory evidence of PE, compared with 15.9% (28/176) patients with ratio >85.

CONCLUSION

These findings support the potential for the use of sFlt1/PlGF and BP measurement alone in resource-limited settings where other laboratory tests or clinical expertise are unavailable for risk stratification. Performance of the biomarker varied by the presence of hypertension and gestational age.

Angiogenic Biomarkers in Preeclampsia

Preeclampsia contributes disproportionately to maternal and neonatal morbidity and mortality throughout the world. A critical driver of preeclampsia is angiogenic imbalance, which is often present weeks to months before overt disease. Two placenta-derived angiogenic biomarkers, soluble fms-like tyrosine kinase 1 (sFlt-1) and placental growth factor (PlGF), have proved useful as diagnostic and prognostic tests for preeclampsia. Recently, the U.S. Food and Drug Administration approved the sFlt-1/PlGF assay to aid in the prediction of preeclampsia with severe features among women with hypertensive disorders of pregnancy at 24-34 weeks of gestation. In this narrative review, we summarize the body of work leading to this approval and describe how the sFlt-1/PlGF ratio may be implemented in clinical practice as an adjunctive measure to help optimize care and to reduce adverse outcomes in preeclampsia.

Translation of mechanistic advances in preeclampsia to the clinic: Long and winding road

As one of the leading causes of premature birth and maternal and infant mortality worldwide, preeclampsia remains a major unmet public health challenge. Preeclampsia and related hypertensive disorders of pregnancy are estimated to cause >75 000 maternal and 500 000 infant deaths globally each year. Because of rising rates of risk factors such as obesity, in vitro fertilization and advanced maternal age, the incidence of preeclampsia is going up with rates ranging from 5% to 10% of all pregnancies worldwide. A major discovery in the field was the realization that the clinical phenotypes related to preeclampsia, such as hypertension, proteinuria, and other adverse maternal/fetal events, are due to excess circulating soluble fms-like tyrosine kinase-1 (sFlt-1, also referred to as sVEGFR-1). sFlt-1 is an endogenous anti-angiogenic protein that is made by the placenta and acts by neutralizing the pro-angiogenic proteins vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). During the last decade, this work has spawned a new era of molecular diagnostics for early detection of this condition. Antagonizing sFlt-1 either by reducing production or blocking its actions has shown salutary effects in animal models. Further, in early-stage human studies, the therapeutic removal of sFlt-1 from maternal circulation has shown promise in delaying disease progression and improving outcomes. Recently, the FDA approved the first molecular test for preterm preeclampsia (sFlt-1/PlGF ratio) for clinical use in the United States. Measuring serum sFlt-1/PlGF ratio in the acute hospital setting may aid short-term management, particularly regarding step-up or step-down of care, decision to transfer to settings better equipped to manage both the mother and the preterm neonate, appropriate timing of administration of steroids and magnesium sulfate, and in expectant management decisions. The test itself has the potential to save lives. Furthermore, the availability of a molecular test that correlates with adverse outcomes has set the stage for interventional clinical trials testing treatments for this disorder. In this review, we will discuss the role of circulating sFlt-1 and related factors in the pathogenesis of preeclampsia and specifically how this discovery is leading to concrete advances in the care of women with preeclampsia.

The value of maternity care in Queensland, 2012-18, based on an analysis of administrative data: a retrospective observational study

OBJECTIVE

To quantify the value of maternity health care - the relationship of outcomes to costs - in Queensland during 2012-18.

STUDY DESIGN

Retrospective observational study; analysis of Queensland Perinatal Data Collection data linked with the Queensland Health Admitted Patient, Non-Admitted Patient, and Emergency Data Collections, and with the Medicare Benefits Schedule (MBS) and Pharmaceutical Benefits Scheme (PBS) databases.

SETTING, PARTICIPANTS

All births in Queensland during 1 July 2012 - 30 June 2018.

MAIN OUTCOME MEASURES

Maternity care costs per birth (reported in 2021-22 Australian dollars), both overall and by funder type (public hospital funders, MBS, PBS, private health insurers, out-of-pocket costs); value of care, defined as total cost per positive birth outcome (composite measure).

RESULTS

The mean cost per birth (all funders) increased from $20 471 (standard deviation [SD], $17 513) during the second half of 2012 to $30 000 (SD, $22 323) during the first half of 2018; the annual total costs for all births increased from $1.31 billion to $1.84 billion, despite a slight decline in the total number of births. In a mixed effects linear analysis adjusted for demographic, clinical, and birth characteristics, the mean total cost per birth in the second half of 2018 was $9493 higher (99.9% confidence interval, $8930-10 056) than during the first half of 2012. The proportion of births that did not satisfy our criteria for a positive birth outcome increased from 27.1% (8404 births) during the second half of 2012 to 30.5% (9041 births) during the first half of 2018.

CONCLUSION

The costs of maternity care have increased in Queensland, and many adverse birth outcomes have become more frequent. Broad clinical collaboration, effective prevention and treatment strategies, as well as maternal health services focused on all dimensions of value, are needed to ensure the quality and viability of maternity care in Australia.