Inflammatory Indices in Preterm Infants with Hemodynamically Significant Patent Ductus Arteriosus: Early Postnatal...

Background: Inflammatory mechanisms may contribute to persistent ductal patency in preterm infants with hemodynamically significant patent ductus arteriosus (hsPDA). This study evaluated early postnatal temporal patterns of complete blood count (CBC)-derived inflammatory indices in relation to ductal status and pharmacologic treatment response. Methods: This retrospective single-center study included preterm infants born at <34 weeks' gestation who received pharmacologic treatment for hsPDA. Hematologic parameters and CBC-derived inflammatory indices, including neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), pan-immune inflammation value (PIV), and immature granulocyte (IG) parameters, were assessed on postnatal days 1, 3, and 7. Results: The final cohort included 71 preterm infants with hsPDA. Over the first postnatal week, NLR and PLR peaked on day 3, MLR remained elevated, and PIV increased toward day 7. SII and SIRI showed significant temporal variation, whereas IG parameters did not. Among longitudinal changes, only ΔPIV, calculated as day 3 minus day 7 values, differed by treatment response, with a greater increase in PIV observed among non-responders. ΔPIV yielded limited discrimination for non-response (AUC = 0.646; sensitivity, 92%; specificity, 37%; cut-off, ≤110.4). Birth weight and gestational age were positively correlated with several hematologic parameters and inflammatory indices, whereas ductal status showed inverse associations with IG% on day 1 and with monocyte count and MLR on day 3. After adjustment for maturational factors and treatment type, the ΔPIV-response association was attenuated, without improved discrimination. Conclusions: CBC-derived inflammatory indices demonstrated distinct early postnatal patterns in infants with hsPDA. ΔPIV may serve as a hypothesis-generating longitudinal marker of treatment response rather than a stand-alone predictor and warrants further validation.