Association of Complete Blood Count Parameters and Systemic Inflammatory Indices with Early Surfactant Administration in Preterm Infants

Background/Objectives: The decision to administer surfactant therapy to preterm newborns is typically based on clinical respiratory findings, oxygen requirements, and the level of respiratory support. The aim of this study was to assess the association of admission complete blood count parameters and derived systemic inflammatory indices with surfactant administration within the first 24 h of life in preterm infants born at ≤32 weeks of gestation, and to evaluate their discriminative performance. Methods: This single-center, retrospective observational cohort study included 100 preterm infants with a gestational age of ≤32 weeks who were admitted to the neonatal intensive care unit between 1 January 2025 and 31 March 2026. The results of the initial complete blood count and blood gas analysis, obtained as part of routine clinical care at admission, were recorded. Systemic inflammatory indices, including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), red cell distribution width-to-platelet ratio (RPR), systemic immune-inflammation index (SII), and mean platelet volume-to-platelet ratio (MPV/PLT), were calculated from the complete blood count results. The primary outcome was surfactant administration within the first 24 h of life. Associated factors were evaluated using logistic regression analysis, and the discriminative performance of continuous variables was assessed using receiver operating characteristic (ROC) curve analysis. Results: Surfactant was administered to 45 infants (45%) within the first 24 h of life. Infants who received surfactant had lower gestational ages, birth weights, 1- and 5 min Apgar scores, partial pressure of carbon dioxide (PCO2), hemoglobin levels, and hematocrit values. No significant differences were observed between groups in NLR, PLR, MLR, RPR, SII, or MPV/PLT. In multivariable analysis, lower gestational age (OR = 0.65; 95% CI: 0.50–0.84; p = 0.001), small-for-gestational-age (SGA) status (OR = 4.61; 95% CI: 1.25–16.91; p = 0.021), and lower 1 min Apgar score (OR = 0.67; 95% CI: 0.46–0.96; p = 0.031) were independently associated with early surfactant administration. Hemoglobin was not independently associated with early surfactant administration after adjustment. In the ROC analysis, the AUC values were 0.804 for birth weight, 0.776 for gestational age, 0.694 for hemoglobin, 0.677 for hematocrit, and 0.640 for PCO2. Conclusions: Lower gestational age, SGA status, and lower 1 min Apgar score were independently associated with early surfactant administration. No significant associations were observed between the evaluated complete blood count-derived inflammatory indices and early surfactant administration. Although hemoglobin and hematocrit levels differed between groups, hemoglobin was not independently associated with the outcome after adjustment. ROC analysis provided descriptive estimates of the discriminative performance of gestational age, birth weight, hemoglobin, hematocrit, and PCO2.