RESUMO
INTRODUCTION: Neonatal infection is a major cause of morbidity in the neonatal period. Several parameters have been used to assess neonatal sepsis. C-reactive protein (CRP) shows high specificity for bacterial infections, but an increase in CRP is often not detected until 12 to 24 hours after onset of the infection. OBJECTIVE: To evaluate the usefulness of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) in the early diagnosis of vertically-transmitted neonatal bacterial infection. METHODS: Thirty-four newborns admitted to the neonatal intensive care unit with an initial diagnosis of respiratory distress were included. Twelve newborns presented the criteria for clinical sepsis or pneumonia (group I) and six had positive blood culture. The remaining patients did not present the clinical criteria for infection (group II). IL-6, TNF-alpha, CRP levels and the ratio between immature and mature neutrophil count were assessed at 8.8 +/- 7.3 hours of life. In 17 patients the same parameters were assessed at 67.4 +/- 24.8 hours of life. The statistical analysis was performed using the Mann-Whitney test. The sensitivity and specificity of these markers were assessed. RESULTS: No differences were found in the perinatal features of either group. Analysis of markers of infection revealed the following significant differences: ratio between immature and mature neutrophil count: (0.25 +/- 0.21 vs 0.12 +/- 0.09; p=0.048), CRP first determination (1.4 +/- 0.8 mg/dL vs 1 +/- 0.5 mg/dL; p=0.036), CRP second determination: (3.8 +/- 1.8 mg/dL vs 1.4 +/- 1.1 mg/dL; p=0.008), IL-6 first determination: (582.2 +/- 810.5 pg/mL vs 31.3 +/- 24.2 pg/mL; p=0.000). Sensitivity/specificity (%): ratio between immature and mature neutrophil count: 41.6/83.6; CRP first determination: 16.6/90.9; CRP second determination: 83.3/87.5; IL-6 (optimum cut-off value: 55 pg/mL): 100/72.7, and TNF-alpha: 16.6/85. CONCLUSIONS: IL-6 determination in the first hours of life is a more sensitive early marker of neonatal infection than other classical markers because of its early elevation. Like CRP, early TNF-alpha determination has high specificity but low sensitivity.