Two biomarkers – pregnancy-associated plasma protein A2 (PAPP-A2) and activin A – when added to relevant clinical information have a better positive predictive value than and a comparable negative predictive value to the currently used ratio of soluble fms-like tyrosine kinase 1 (sFlt-1) to placental growth factor (PlGF), new research suggests.
The third-trimester sFlt-1:PlGF ratio can predict short-term absence of preeclampsia. By contrast, , according to the authors.
Preeclampsia has “potentially devastating maternal and fetal complications, [including] significantly increased cardiovascular risk for affected women later in life,” study author Stella S. Daskalopoulou, MD, PhD, associate professor of medicine at McGill University Health Centre in Montreal, said in an interview.
“A more accurate prediction of preeclampsia is expected to improve risk stratification and clinical care and shape clinical practice guidelines,” she said.
The study was published online in the Canadian Journal of Cardiology.
Better predictive value
For a prospective cohort study, the investigators recruited 192 women with first-trimester high-risk singleton pregnancies from tertiary obstetric clinics in Montreal.
At baseline, they collected clinical information, including height, prepregnancy weight, personal and family medical history, and medication use.
At each trimester, blood pressure was measured, and blood samples were collected to quantify sFlt-1, PlGF, PAPP-A2, PAPP-A, activin A, inhibin A, follistatin, and glycosylated fibronectin. For the sFlt-1:PlGF ratio, the researchers used a cutoff point of 38, based on prior evidence. Because there are no agreed-upon cutoff points for the other biomarkers, they chose cutoff points that maximized sensitivity and specificity.
Pregnancies were considered high risk if the mother had any of the following conditions: prepregnancy BMI ≥ 25, maternal age ≥ 35 years, chronic hypertension, diabetes, renal disease, conception via in vitro fertilization, or maternal or first-degree family history of preeclampsia.
The primary outcome was preeclampsia, which was defined according to the Society of Obstetrics and Gynecology guidelines as systolic blood pressure ≥ 140 mm Hg or diastolic blood pressure of ≥ mm Hg together with either proteinuria or maternal end-organ dysfunction.
A total of 18 women (9.38%) developed preeclampsia. Those women had higher blood pressure at baseline (although it was within normal limits) and were more likely to have preexisting diabetes or a previous pregnancy with preeclampsia. They were also more likely to report Black race. Serum levels of PAPP-A, PAPP-A2, activin A, and inhibin A were significantly different between patients who developed preeclampsia and those who did not. These levels were increased throughout pregnancy.
Alongside the sFlt-1:PlGF ratio, two biomarkers, PAPP-A2 (odds ratio, 1.78) and activin A (OR, 1.84), were significantly associated with the primary outcome after adjustment for age, prepregnancy BMI, race, and mean arterial pressure.
When added to a model that included those clinical factors, a positive third-trimester result for both PAPP-A2 and activin A had a better positive predictive value than the sFlt-1:PlGF ratio added to the clinical model (91.67% vs. 66.67%). The two biomarkers also had a negative predictive value that was comparable to that of the sFlt-1:PlGF ratio (97.69% vs. 96%).
Study limitations include the small sample size and missing covariates for some participants. Furthermore, the findings cannot be generalized to low-risk populations.
“Whereas the third-trimester sFlt-1:PlGF ratio can predict short-term absence of preeclampsia, PAPP-A2 and activin A had both high positive and negative predictive values and thus could serve as biomarkers to predict the occurrence (and absence) of preeclampsia; these findings will be validated in future studies,” the authors concluded.
Dr. Daskalopoulou said that her group is currently performing a large multinational study, PULSE, “which will be the ideal platform to validate and extend our findings. The aim of the study is to predict preeclampsia using a multimodal approach that includes arterial stiffness measurements and blood biomarkers.”
She expanded on the potential benefits of this research. “Finding an accurate predictive tool would not only help design appropriate early care plans for truly high-risk pregnant women, including monitoring and delivery planning, but also facilitate the development of novel strategies for the prevention and treatment of preeclampsia, improving the life of millions of young mothers and their offspring around the world.”