C-reactive protein to platelet ratio as an early biomarker in differentiating neonatal late-onset sepsis in neonates with pneumonia

Neonates with pneumonia (NWP) may experience unidentified life-threatening sepsis, yet distinguishing NWP from neonates with sepsis (NWS) based solely on clinical presentation remains challenging. This study aimed to evaluate the diagnostic utility of the C-reactive protein to platelet ratio (CPR) in distinguishing neonatal late-onset sepsis (LOS) among NWPs. From February 2016 to March 2022, a total of 1385 NWPs aged over 3 days were included. Of these, 174 neonates with confirmed positive blood cultures were categorized into the sepsis cohort, while the remainder formed the pneumonia cohort. All clinical data were retrospectively extracted from electronic medical records. CPR was calculated as the ratio of C-reactive protein levels to platelet count. Independent risk factors (IRFs) for neonatal LOS were identified through multivariate logistic regression. The diagnostic performance of CPR in identifying LOS among NWPs was analyzed using receiver operating characteristic (ROC) curve metrics. Statistical analyses were conducted using SPSS version 24.0 and MedCalc version 15.2.2. Neonates with NWS demonstrated significantly higher CPR compared to those with NWP alone. Further analysis revealed a notably increased incidence of sepsis among neonates exhibiting elevated CPR levels relative to those with lower values. Correlation analysis identified a direct association between CPR and elevated procalcitonin, creatinine, and urea nitrogen levels, as well as prolonged hospitalization. Multiple logistic regression analysis identified CPR as an IRF for late-onset NWS. ROC curve analysis demonstrated that CPR outperformed CRP and platelet count individually in diagnosing NWS, with a diagnostic sensitivity of 54% and specificity of 85%. CPR serves as an effective initial diagnostic marker with superior accuracy in distinguishing delayed NWS from NWP compared to CRP and platelet count alone.