Evaluation of the CALLY Index and Neutrophil-to-Lymphocyte Ratio, Platelet-to-Lymphocyte Ratio, Systemic Immune-Inflammation Index, and Systemic Inflammation Response Index in Predicting Birth Latency in Preterm Labor

To evaluate the predictive value of hematological indices—including the C-reactive protein–albumin–lymphocyte (CALLY) index, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI)—for identifying delivery within 48 h in women with preterm labor. This retrospective cohort study included 213 singleton pregnancies diagnosed with preterm labor between January 2023 and January 2024. Maternal peripheral blood samples were collected at admission before intervention. Participants were categorized by latency to delivery (< 48 h vs. ≥48 h). Hematologic parameters and inflammatory indices were compared, and predictive performance was assessed using ROC analysis and multivariate logistic regression. Among the 213 women, 94 (44.1%) delivered within 48 h. Women who delivered within 48 h had a lower gestational age at diagnosis and birth, a higher rate of respiratory distress syndrome (RDS), higher SIRI, NLR, SII, and PLR values, and a lower CALLY index (all p < 0.05). Gestational age at diagnosis showed the greatest predictive performance (AUC = 0.738), whereas SIRI demonstrated the highest discriminatory ability among the inflammatory indices (AUC = 0.651). Although several inflammatory indices were significantly associated with delivery within 48 h in the univariate analyses, only gestational age at diagnosis remained an independent predictor in the multivariable model. The multivariable model demonstrated moderate discriminatory performance (AUC = 0.803, 95%CI 0.744–0.862). Hematological indices demonstrated only limited predictive performance and did not provide independent predictive value beyond gestational age at diagnosis. Gestational age remained the strongest predictor of delivery within 48 h, suggesting that inflammatory indices may serve only as complementary rather than standalone predictive markers.