Test Gives Mixed Results for Preeclampsia Risk in SLE

WASHINGTON, DC — A diagnostic test to predict preeclampsia does not effectively rule in or out this pregnancy complication in women with systemic lupus erythematosus (SLE) and proteinuria, according to new research presented at the American College of Rheumatology (ACR) 2024 Annual Meeting.
“If you have a patient who has proteinuria during pregnancy, I’m not sure we know what to do with this test,” said Megan Clowse, MD, MPH, associate professor of medicine and chief of the Division of Rheumatology and Immunology at Duke University School of Medicine in Durham, North Carolina. She led the research and presented the work.
The results “are probably a step in the right direction to understanding that we need more biochemical markers for differentiating preeclampsia [in this patient population],” Leanna Wise, MD, of the Keck School of Medicine at the University of Southern California, Los Angeles, told Medscape Medical News. She co-moderated the session where the research was presented. “It exposed that we have a lot of gray areas in which we need to do more research.”
The test is a ratio of two biomarkers that measure spiral artery and placental health: Soluble fms-like tyrosine kinase 1 (sFlt-1) and placental growth factor (PlGF). In the general population, a sFlt-1/PlGF ratio ≤ 38 effectively rules out the short-term risk for preeclampsia, whereas a ratio ≥ 85 is moderately predictive of preeclampsia. However, it was not known how this test would fare in pregnant women with SLE who are already at a higher risk for the complication.
To answer this question, Clowse and colleagues pulled patient data from an ongoing prospective registry of lupus pregnancies. The analysis included patients with a confirmed SLE diagnosis who had enrolled in the registry prior to 30 weeks’ gestation. All participants had provided a serum sample prior to 16 weeks’ gestation and had singleton pregnancies.
In an extensive chart review, preeclampsia was determined by a roundtable of six experts: Two rheumatologists, two maternal-fetal medicine doctors, and two nephrologists.
The analysis included 79 pregnancies, of which 30% developed preeclampsia. Nearly half (47%) of the participants identified as Black or African American. About 30% had a history of lupus nephritis, and half of these patients had active disease during their pregnancy. About half of the women reported that this was their first pregnancy, and an additional 17% of women reported a prior episode of preeclampsia. Most patients were on aspirin (92%) and hydroxychloroquine (87%), and another 43% were prescribed prednisone and 37% were taking azathioprine.
Researchers assessed whether a low sFlt-1/PlGF ratio (≤ 38) was associated with the absence of preeclampsia at 4- and 8-weeks post–blood draw, as well as during the entire pregnancy. They also tested if a high ratio (≥ 85) was associated with the development of preeclampsia within 4- and 8-weeks post–blood draw and through the entire pregnancy.
Across all pregnancies in the cohort, those with sFlt-1/PlGF ≤ 38 were unlikely to develop preeclampsia at 4 weeks post-draw (negative predictive value [NPV], 98%) and 8 weeks post-draw (NPV, 96%). Still, 20% of patients with this low ratio went on to develop preeclampsia at some point during their pregnancy.
Similar to the general population, sFlt-1/PlGF ≥ 85 was only moderately predictive of preeclampsia. Over half of all patients with this high ratio developed preeclampsia, but more than 40% did not.
Researchers also stratified patients by urine protein:creatinine ratio (UPCR) at the time of their rheumatology visit, defining proteinuria as a UPCR ≥ 300 mg/g.
In patients without proteinuria (n = 63), a low sFlt-1/PlGF ratio ruled out preeclampsia over the next 8 weeks, but a high sFlt-1/PlGF ratio was not usefully predictive of preeclampsia.
Low Ratio to Rule Out Preeclampsia ‘Reassuring’
The high reliability in ruling out preeclampsia in this subset of patients with a low sFlt-1/PlGF ratio is “reassuring,” Wise said, and suggests that these patients are “relatively safe moving forward,” given regular follow-up.
In the small group of patients with proteinuria (n = 16), 44% ultimately developed preeclampsia. One third of patients with sFlt-1/PlGF ≤ 38 developed preeclampsia in 8 weeks, and half experienced preeclampsia at some point during their pregnancy. Among the patients with sFlt-1:PlGF ≥ 85, 56% developed preeclampsia during their pregnancy.
“The negative predictive values are not really great, and the positive predictive values are not really very useful,” Clowse said. For a pregnant patient with proteinuria, “I don’t think that a high [ratio] is going to tell us that she definitely has preeclampsia today or tomorrow. I also am not convinced yet that a low [ratio] tells us that she’s out of the woods. So, I think we definitely need more research on what to do with this test in patients with proteinuria.”
Clowse is a consultant and has received research support/grants from GSK and UCB. She also reported consulting for AstraZeneca. Wise is a consultant for Aurinia Pharmaceuticals and has received honoraria from AstraZeneca, Aurinia Pharmaceuticals, and GSK.
 
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