The Delta Neutrophil Index as a predictive marker of histological chorioamnionitis in patients with preterm premature rupture of membranes: A retrospective study

BACKGROUND Histological chorioamnionitis (HCA) is related to perinatal morbidity. However, there is no definite diagnostic method for detecting chorioamnionitis before delivery. METHODS We evaluated whether the delta neutrophil index (DNI) was an effective early marker of HCA in patients with preterm premature rupture of membranes (PPROM). We retrospectively evaluated 149 women diagnosed with PPROM (gestational age, 20+0 to 36+6 weeks) at Severance Hospital from January 2013 to December 2014. The women were categorized into the following two groups: (a) PPROM without HCA and (b) PPROM with HCA. The maternal white blood cell (WBC) count, neutrophil-to-lymphocyte ratio (NLR), C-reactive protein (CRP) level, and DNI were measured at admission. The DNI has been reported to reflect the fraction of circulating immature granulocytes associated with infection. RESULTS Of the 149 patients, 87 were included in the PPROM without HCA group and 62 were included in the PPROM with HCA group. The interval between admission and delivery was significantly shorter in the PPROM with HCA group than in the PPROM without HCA group. There was no significant difference in the maternal WBC count. The serum CRP level, NLR, and DNI were significantly lower in the PPROM without HCA group than in the PPROM with HCA group, while the lymphocyte count was significantly lower in the PPROM with HCA group than in the PPROM without HCA group. A predictive equation was generated by combining the DNI, lymphocyte count, and CRP level, and the sensitivity and specificity for predicting a placental inflammatory response were 69.1% and 70.5%, respectively. CONCLUSIONS The DNI could be a predictive marker for HCA in patients with PPROM. Our predictive equation involving the DNI, lymphocyte count, and CRP level may be helpful for predicting the placental inflammatory response in patients with PPROM.