Physicians, midwives, and others caring for women with pregnancy-related hypertension will soon have a new tool at their disposal. In May, the Food and Drug Administration granted marketing authorization to BRAHMS GmbH, part of Thermo Fisher Scientific, for a blood test that can help clinicians better assess a patient's risk of progressing to severe preeclampsia.
Preeclampsia is a disorder in which women who previously had normal or moderately elevated blood pressure develop dangerously high blood pressure in the later stages of pregnancy. It poses risks for both mother and infant and is a leading cause of maternal death in the United States. The only remedy is early delivery of the baby.
Rates of preeclampsia and eclampsia (a later, more severe stage of the disorder) grew by 21% from 2005 to 2014, when almost 5% of all U.S. inpatient deliveries involved these conditions. The rate for Black women was 70 per 1,000 deliveries in 2014, 60% higher than the rate for White women. The condition may have contributed to the recent death of Olympic track and field gold medalist Tori Bowie, who died from complications of childbirth earlier this year. Preeclampsia also affects American Indian/Alaskan Native women at especially high rates.
The new test is designed for use in pregnant patients who are already hospitalized for elevated blood pressure and some other hypertensive disorders. The test looks at the ratio of two placental biomarkers: placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1). According to a study of the blood test by Thadhani and colleagues in the November 9, 2022, issue of NEJM Evidence, women with high ratios of sFlt-1 to PlGF in their blood were more likely to progress to severe preeclampsia within two weeks of testing and experience adverse maternal outcomes. Adverse fetal and neonatal outcomes were also more prevalent in women with high test ratios.
The test can aid clinicians in determining which preeclampsia patients need to remain in the hospital for observation and which can safely return home to continue their pregnancies. Test ratios of 40 or more had a positive predictive value of 65%, "surpassing routine measures currently used to predict [development of severe preeclampsia]," the study authors reported. Ratios below 40 had a 96% negative predictive value.
The researchers studied the test's prognostic value using blood samples from more than 1,000 women at 18 U.S. sites. Almost a third (31%) of study enrollees were Black and 16% were Hispanic. All had a hypertensive disorder of pregnancy at 23 to 35 weeks of gestation.
Although far less common, preeclampsia can also occur or become apparent up to six weeks after delivery. The study did not investigate use of the test in postpartum women.-Nicole Fauteux