Objective To determine through serial measurements the sensitivity and specificity of biological markers: C-reactive protein (CRP), interleukin-6 (IL-6), and elastase-α1-proteinase inhibitor (E-α1-PI) in early, pre-symptomatic diagnosis of neonatal infections, as well as prognostic significance of these markers.

Methods 93 newborns were examined and divided in the following groups: proven early sepsis, proven late sepsis, suspected infection, and a control group. Serial measurements were performed: in the first 24 hours, in 48 hours and every following day afterwards. A quantitative method for CRP and ELISA were used. Statistical analysis was performed using Friedman, Mann–Whitney U and Wilcoxon test.

Results The obtained results showed statistically significant (p<0.001) early increase of IL-6 in the group with sepsis contrary to CRP and E-α1-PI that increased significantly (p<0.001) during the following measurements compared to the control group. Simultaneous use of IL-6 and CRP revealed highest sensitivity (87%) and specificity (96%) in early diagnosis of neonatal infection. Serial measurements of E-alpha1-PI showed an improvement in cases of good response to therapy and a rapid decrease when the condition worsened.

Conclusions There is an apparent need for serial use of markers for early diagnosis and monitoring of neonatal infections. Simultaneous use of IL-6 and CRP showed highest sensitivity and specificity. E-α1-PI appeared as a good marker for chronological follow up of the infection, response to therapy and complications’ development.