Threshold-dependent effect of the neutrophil-to-albumin ratio (NAR) in early pregnancy: a novel insight for preeclampsia risk prediction.

objectivePreeclampsia (PE) is a major cause of adverse outcomes in pregnant, postpartum, and perinatal women; however, its early identification remains a clinical challenge, particularly in resource-scarce regions. The neutrophil-to-albumin ratio (NAR) reflects both systemic inflammatory response and nutritional status and has recently emerged as a promising early biomarker. This study aimed to investigate the association between NAR and subsequent PE risk and to compare its predictive efficacy with that of placental growth factor (PlGF) and mean arterial pressure (MAP).

methodsThis retrospective cohort study enrolled 11,916 pregnant women with a gestational age of < 14 weeks. Logistic regression, restricted cubic spline (RCS), and two-stage regression analyses were applied to assess the association between NAR and PE. The diagnostic performance of NAR, PlGF, and MAP was compared using receiver operating characteristic (ROC) curve analysis.

resultsAfter adjustment for maternal factors, elevated NAR was independently associated with an increased risk of PE (adjusted odds ratio [OR] = 2.04; 95% confidence interval [CI]: 1.42-2.92; P < 0.001). RCS analysis identified a nonlinear threshold at log-transformed NAR (LN[NAR]) = -1.92, beyond which PE risk increased sharply (OR = 4.26; 95% CI: 1.99-9.13). LN(NAR) and PlGF demonstrated comparable discriminative ability (area under the curve [AUC] = 0.591 vs. 0.605) but were inferior to MAP (AUC = 0.710). The correlation between NAR and PlGF was weak (r = 0.05).

conclusionElevated LN(NAR) is independently associated with PE in a threshold-dependent manner. In resource-limited settings, NAR may serve as a practical early PE biomarker for PE or as a component of multimodal prediction models.