BNP-Derived Uric Acid Composite Indices for the Evaluation of Dyspnea in Third-Trimester Pregnancy: A Prospective Emergency Department Study.

Background: Dyspnea is common in pregnancy and difficult to assess in the emergency department (ED), as it may reflect physiological adaptation or cardiopulmonary pathology. We evaluated whether novel BNP-derived uric acid composite indices aid the assessment of dyspnea in late pregnancy; to our knowledge, this is the first study of such indices in this setting. Methods: In this prospective observational study, third-trimester pregnant women (≥27 weeks) presenting to the ED with dyspnea were compared with age-matched asymptomatic pregnant controls. All underwent laboratory testing (including BNP, D-dimer, and uric acid) and standardised transthoracic echocardiography. Three composite indices were calculated (BNP/Albumin, BNP/Uric acid, and BNP × Uric acid), and diagnostic performance was assessed by receiver operating characteristic (ROC) analysis. Results: A total of 215 women were included (100 dyspnea, 115 controls). The dyspnea group had significantly higher D-dimer, BNP, uric acid, and all three composite indices (all p < 0.001), together with higher systolic pulmonary artery pressure (sPAP), right atrial and ventricular diameters, and lateral E/e'. Uric acid (AUC 0.998), the BNP × Uric acid product (AUC 0.846), and sPAP (AUC 0.836) showed the strongest discrimination; the BNP × Uric acid product outperformed BNP, D-dimer, and BNP/Albumin individually but did not surpass uric acid alone. Conclusions: Dyspneic third-trimester women show subtle but significant cardiopulmonary changes despite values that largely remain within normal ranges. These changes distinguished symptomatic from asymptomatic pregnancy but remained largely within normal ranges and do not by themselves identify acute cardiopulmonary disease; uric acid alone was the strongest discriminator, and the composite indices are proposed only as hypothesis-generating tools requiring external validation, ideally against dyspnoeic pregnant women with confirmed pathology.