USA: A detectable NT-proBNP may be helpful to identify patients with chronic hypertension (cHTN) at high delivery risk within 2 weeks from superimposed preeclampsia (SI preE), finds a recent study. Also, NT-proBNP is a predictor of SI preE, and thus may be a useful tool to guide the optimal timing of interventions (antenatal corticosteroids).
The study was published in the American Journal of Obstetrics & Gynecology and will be subsequently presented at the Oral concurrent session 8 on February 5, 2022.

Differentiating between normal physiologic fluctuations of blood pressure among pregnant patients with cHTN versus SI preE is a common clinical conundrum. Increased cardiac afterload due to increased systemic vascular resistance reflected by N-terminal pro-B-type natriuretic peptide (NTproBNP) is a unique marker of preE. Megan C. Oakes, Washington University in Saint Louis, St. Louis, MO, and colleagues, therefore, aimed to evaluate the utility of NT-proBNP to discriminate between cHTN and SI preE in a prospective cohort study.
The study included patients with singleton pregnancies ≥ 20 weeks' gestation with known cHTN undergoing evaluation for SI preE at a tertiary care center. Also, NT-proBNP was obtained at the same time as other laboratory tests sent for preE evaluation. The primary outcome was SI preE, based on the clinician's documentation during the index evaluation.
The predictive ability of a detectable NT-proBNP (≥ 50 pg/mL) for SI preE was assessed using the receiver operating characteristic curves. The time to delivery within 14 days between patients with and without a detectable NT-proBNP was compared. The planned sample size was 52, based on α 0.05, β 0.2, and effect size of 0.8 for the primary outcome.

Based on the study, the researchers found the following:
Of 59 patients enrolled in the study, 24 (40.7%) were diagnosed with SI preE during evaluation.
The AUC for a detectable NT-proBNP was 0.72 for the diagnosis of SI preE.
The optimal NT-proBNP cut-off was 102.5 pg/mL, with positive and negative predictive values of 28.6% and 57.7%, respectively.
In a sensitivity analysis of 3rd trimester pregnancies, the predictive value of NT-proBNP improved (AUC 0.77).
Patients with a detectable NT-proBNP had a significantly shorter time to delivery compared to those with an undetectable NT-proBNP.
To conclude, a detectable NT-proBNP is a predictor of SI preE and may be helpful in identifying patients with cHTN at high risk for delivery within 2 weeks from SI preE. Thus, it may be a useful tool to guide optimal timing of interventions such as antenatal corticosteroids.
Reference:
The study titled, "Deciphering chronic hypertension from preeclampsia: Utility of NT-proBNP in obstetric triage," was published in the American Journal of Obstetrics & Gynecology.
DOI: https://doi.org/10.1016/j.ajog.2021.11.063