Thymic involution as a predictor of early-onset neonatal sepsis

Background: Diagnosis of early-onset neonatal sepsis (EONS) is often difficult because of vague clinical signs and non-specific laboratory parameters. Objective: To assess the statistical validity of thymic size estimation as a diagnostic marker of EONS compared with cord blood interleukin-6 (IL-6) concentrations. Subjects and Methods: Thirty-two neonates delivered in hospital and admitted to the neonatal unit with EONS comprised the study group. EONS was diagnosed on the basis of development of clinical signs and symptoms of sepsis within 72 hours of birth in the presence of antenatal risk factors for chorio-amnionitis and a positive blood culture. Thirty-two gestational age- and gender-matched healthy neonates served as controls. Cord blood IL-6 concentrations were estimated by ELISA. Thymic size was assessed by sonological measurement of thymic dimensions (longitudinal and transverse diameters, thymic volume and thymic index) within 24 hours of birth in the study infants and the controls. Data were analyzed by SPSS 16.0. Results: Thymic size was significantly smaller whereas cord blood IL-6 concentrations were significantly higher (P<0.001) in the sepsis group than in the controls. Sensitivity and specificity of thymic dimensions were comparable to IL-6 concentrations for diagnosing EONS. Significant correlation was noted between reduction in thymic size and a rise in IL-6 concentrations. Conclusion: Thymic involution can be used as a reliable diagnostic marker for EONS.