Preeclampsia Flagged by Common Lab Values

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Can the fibrinogen-to-albumin ratio help with early identification?

by
Nicole Lou, Senior Staff Writer, MedPage Today
October 20, 2024

PHILADELPHIA — Existing blood tests may help identify pregnant women at risk of developing preeclampsia, researchers found from a retrospective chart review.

Calculated from lab values taken at admission for labor, the fibrinogen-to-albumin ratio (FAR) emerged as an independent marker for severe preeclampsia (OR 18.49, 95% CI 1.70-200.67) in a single-center study by Lucy Shang, a medical student at the Icahn School of Medicine at Mount Sinai in New York City, and colleagues.

After adjustment on multivariable logistic regression analysis, the inflammatory marker remained predictive of any preeclampsia (OR 37.38, 95% CI 7.65-182.70) regardless of hemoglobin, liver enzymes, age, race, gravidity, and multiple gestations, Shang reported at the American Society of Anesthesiologists (ASA) annual meeting.

FAR is already gaining attention for predicting outcomes in settings such as rheumatoid arthritis, heart disease, and stroke.

“While FAR has been associated with other inflammatory conditions, its specific application to preeclampsia and preeclampsia with severe symptoms has not been reported in a group this large and racially diverse,” Shang said in an ASA press release.

“Our study shows that FAR can be a predictive tool that gives anesthesiologists and obstetricians a new method for assessing a laboring mom’s risk of developing preeclampsia when they are admitted to the hospital,” Shang added. “Additional research is needed to determine the exact range of the FAR that would be considered concerning and would be helpful to incorporate into routine prenatal care as a predictive tool for early identification of preeclampsia.”

Outside experts contacted by MedPage Today agreed with the need for more research on the potential role of FAR before attempting to implement it in this setting.

Connie Graves, MD, of Tennessee Maternal Fetal Medicine in Nashville, nevertheless said the study results are “plausible” and that the advantage of the FAR approach would be that “these are common labs that we obtain on a regular basis and do not require special equipment.”

These values are known to change during pregnancy, however, Graves warned.

“It is unclear how early FAR can be tested to for prediction of the later development of preeclampsia,” noted Carla Janzen, MD, PhD, of the University of California Los Angeles.

Janzen suggested that the current study at least supports existing evidence that “when sampled, there are surprising derangements in the immune-related hematological physiology with severe preeclampsia.”

She urged that these findings be validated prospectively in high-risk people. This includes non-Hispanic Black women, who are disproportionately affected by preeclampsia and other hypertensive disorders of pregnancy and experience the highest mortality from these conditions based on CDC research.

Indeed, Shang’s group reported that African-American race was another significant predictor of preeclampsia (OR 1.77, 95% CI 1.41-2.23) and severe preeclampsia (OR 1.5, 95% CI 1.03-2.16) in their retrospective study.

Preeclampsia is one of the leading causes of maternal and fetal morbidity and mortality, occurring in 3% to 7% of all pregnancies. This inflammatory condition of high blood pressure (BP) coupled with liver or kidney damage, occurring in women after the 20th week of pregnancy or postpartum, is believed to originate in the placenta and can progress rapidly and cause organ damage, stroke, preterm birth, and slow growth in the baby.

Once preeclampsia is diagnosed, it may be managed with frequent monitoring — but the only treatment is delivery.

To prevent preeclampsia, the American College of Obstetricians and Gynecologists recommends low-dose aspirin for high-risk pregnant patients with one or more particular risk factors such as chronic high BP, type 1 or 2 diabetes before pregnancy, or kidney disease.

Study Details

Shang and colleagues reviewed records of the 2,629 women who gave birth from 2018 to 2024 at their institution. Participants were included if they had fibrinogen and albumin lab values upon admission for labor.

These women were split into groups with no preeclampsia (n=1,819), preeclampsia with mild features (n=584), and preeclampsia with severe features (n=226).

The severe preeclampsia group had significantly higher BMI (33.0) and BP (median 153/91 mmHg) compared with the other groups. This group had disproportionately lower gestational age (37 weeks) as well.

Hemoglobin, liver enzymes alanine transaminase (ALT) and aspartate transaminase (AST), and age were significant predictors of any preeclampsia alone (not severe preeclampsia).

A multivariate model combining these values with the FAR labs resulted in an area under the curve (AUC) of 0.598 for predicting preeclampsia — though modest, this was still better than the AUC for any single variable alone, according to Shang.

Louise Laurent, MD, PhD, of the University of California San Diego, cautioned that the current report lacked important details such as the time between the blood draw where the fibrinogen and albumen values were measured and the diagnosis of preeclampsia.

She noted that neither fibrinogen nor albumin are truly routinely measured in pregnancy across institutions.

“I would worry that the values available on retrospective chart review are from patients who were suspected to have preeclampsia or have risk factors for preeclampsia, unless the institution had implemented routine testing at a specific gestational age,” Laurent told MedPage Today. Gestational age itself should have been among the factors adjusted for in the authors’ model, she added.

Encouraging Data

“Happily, this type of retrospective study can now be repeated in larger cohorts and other centers based on electronic medical records, following appropriate ethical review procedures. Investigating the potential utility of FAR in prospectively collected samples would be a next step to see how well the test may work, but these results should encourage the authors and other researchers to take these next steps,” commented William Ackerman, MD, of the University of Illinois Chicago.

Shang said her group is hoping to work with a larger multicenter dataset before embarking on a prospective study.

For now, no guideline-recommended test exists in early pregnancy to predict imminent preeclampsia. Previously, another group had identified a cell-free RNA signature that showed promise in predicting preeclampsia several weeks before the onset of symptoms.