Background The neutrophil-lymphocyte ratio (NLR) is easily calculated blood test parameter, which can be used as marker to predict many inflammatory disorders. The aim of this study was to assess and compare the NLR in maternal blood with the white blood cell (WBC) count and C-reactive protein (CRP) concentration for the prediction of histological chorioamnionitis. Methods This was a case-control study of 137 woman with preterm premature rupture of membranes (PPROM) at a gestational age between 22+ 0 and 34+ 6 weeks. Blood samples, collected less than 48 h before delivery and at least 48 h after the administration of corticosteroids, were selected for the analysis. The NLR was calculated by dividing the number of neutrophils by the number of lymphocytes. Chorioamnionitis was diagnosed by the histopathological evaluation of placental membranes and chorionic plate. Results Patients with diagnosed histological chorioamnionitis (HCA) had significantly higher levels of WBC, CRP and NLR (p-value < 0.001). Levels of WBC, CRP and NLR predicted HCA with an area under the curve (AUC) of 0.81, 0.81 and 0.89, respectively. NLR had statistically significantly higher AUC than WBC, but no significant difference was found between AUCs of NLR and CRP. The cut-off level of NLR was found to be 5,97, which had a sensitivity of 77 % and a specificity of 95 %. Conclusion NLR has a good predictive value for HCA and could be used as an additional diagnostic marker for predicting histological chorioamnionitis in cases with preterm premature rupture of membranes before 34 weeks of gestation.

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