A new blood test might help doctors identify pregnant women who are unlikely to develop a dangerous complication called pre-eclampsia, despite having suspicious signs or symptoms.
That's the finding of a study in the Jan. 7 issue of the New England Journal of Medicine.
Experts said that if the results are confirmed by further research, the test could go a long way in ruling out pre-eclampsia in women with suspected cases.
That's important because right now, women with possible pre-eclampsia are usually hospitalized for close monitoring, said Dr. Ellen Seely, of Brigham and Women's Hospital in Boston.
A reliable test that could spare women that hospital stay would have a "substantial impact," said Seely, who wrote an editorial published with the study.
Anywhere from 2 percent to 8 percent of pregnant women develop pre-eclampsia, according to the March of Dimes.
The condition, which occurs after the 20th week of pregnancy, is marked by high blood pressure and other signs that a woman's organs -- such as the kidneys and liver -- aren't functioning properly. Symptoms can include protein in the urine, as well as severe headaches and vision problems.
Detecting pre-eclampsia early is "essential," because it carries serious risks for mothers and babies, said Dr. Stefan Verlohren, senior researcher on the new study and a consultant in maternal/fetal medicine at Charite University Medicine, in Berlin, Germany.
Pre-eclampsia can lead to preterm delivery and low birth weight. It also raises a woman's risk of seizures and coma, and placental abruption -- where the placenta separates from the uterus, sometimes causing life-threatening bleeding.
The problem, Verlohren said, is that it can be difficult to know when a woman is developing pre-eclampsia. For example, women who show elevated blood pressure later in pregnancy could be in the early stages of pre-eclampsia, or they could have isolated high blood pressure.
So his team looked at whether a blood test could help predict whether women with suspected pre-eclampsia would be diagnosed with the disorder in the next week.
The test measures the ratio of two proteins in the blood. One, called sFlt-1, inhibits new blood vessels from forming; the other, known as PlGF, encourages blood vessel formation. Studies have shown that women with pre-eclampsia tend to have high levels of sFlt-1, but relatively low levels of PlGF -- a sign of compromised blood flow to the placenta.
Verlohren's team used blood samples from more than 1,000 women who were between the 24th and 37th week of pregnancy, all of whom had suspected pre-eclampsia.
Each woman had at least one sign or symptom of the complication, but did not meet the criteria doctors use to definitively diagnose it, Verlohren said.
In a first group, of 500 women, the researchers found that a test result of 38 appeared to be the key cutoff number. They then validated that in another 550 patients.
It turned out that women with a test result of 38 or lower remained free of pre-eclampsia for the next week more than 99 percent of the time, the investigators found.
"This is a test that can tell a woman she's extremely unlikely to develop pre-eclampsia in the next week," Seely said.
But what it can't do, she added, is predict which women will develop the complication. Only about 37 percent of study patients with a result higher than 38 developed pre-eclampsia in the next four weeks.
It's also unclear how exactly the test should be used in the real world. "This study does not address the question of how to use it in practice," Seely said.
For one, it reliably ruled out pre-eclampsia, but only for the next week. Seely said it's not known whether the test would continue to perform as well if a woman were retested after a week.
Verlohren said a clinical trial is underway in the United Kingdom to see whether the test -- with its one-week prediction -- can reduce unnecessary hospital stays for pre-eclampsia monitoring.
The test's manufacturer, Roche Diagnostics, funded the new study, and Verlohren and several co-researchers have financial ties to the company.
If the test can help many women avoid the hospital, the benefits would be significant, Seely said.
"Hospitalization takes women away from their families, including any children they have at home," she pointed out. "The stress is substantial. If that can be avoided it would have a big impact on their quality of life."
