<b>Correlation of Plasma Lactate Levels with Neonatal Birth Asphyxia as Diagnostic Tool</b>

Background: Birth asphyxia remains a leading cause of neonatal morbidity and mortality worldwide, contributing significantly to hypoxic-ischemic encephalopathy and long-term neurodevelopmental impairment. Rapid, accurate diagnosis is essential, yet current clinical and biochemical tools, such as the APGAR score and cord blood pH, have limitations in sensitivity, objectivity, and accessibility. Plasma lactate, a marker of anaerobic metabolism, has emerged as a potential early indicator of perinatal hypoxia. Objective: To determine the diagnostic accuracy of plasma lactate levels measured at six hours of life in identifying neonatal birth asphyxia. Methods: This quasi-experimental study was conducted at the Neonatology Department, Combined Military Hospital Rawalpindi, from July to December 2023. Seventy neonates (≥34 weeks gestation) were enrolled and classified into asphyxiated (APGAR <5 at 5 minutes, n=18) and non-asphyxiated (APGAR ≥5, n=52) groups. Peripheral arterial plasma lactate was measured at six hours using a COBAS B 221 analyser. Sensitivity, specificity, and predictive values were calculated. Results: Mean plasma lactate was significantly higher in asphyxiated neonates (5.97 ± 0.89 mmol/L) than in non-asphyxiated neonates (2.20 ± 0.66 mmol/L; p<0.001), with large effect size. Sensitivity was 100.0% (95% CI 81.5–100.0) and specificity 96.2% (95% CI 86.8–99.5); PPV and NPV were 90.0% and 100.0%, respectively. Conclusion: Plasma lactate measured at six hours is a highly sensitive and specific biomarker for diagnosing neonatal birth asphyxia and may serve as a valuable adjunct to clinical assessment.