Maternal serum interleukin-6 concentrations in patients with preterm premature rupture of membranes and evidence of infection

OBJECTIVE: Our purpose was to determine whether maternal serum interleukin-6 concentrations are elevated in patients with preterm premature rupture of membranes and intrauterine infection. STUDY DESIGN: By use of a sensitive enzyme-linked immunosorbent assay maternal serum interleukin-6 concentrations were measured in 110 samples from patients at 22 to 34 weeks gestation with the following conditions: nonlaboring, uninfected controls (n = 46), preterm premature rupture of membranes >48 hours before delivery without infection (n = 27), preterm premature rupture of membranes 24 to 38 hours before delivery with subsequent clinical or histologic infection (n = 11), and preterm premature rupture of membranes <24 hours before delivery with infection present by clinical or histologic criteria (n = 26). The Mann-Whitney U test was used for statistical analysis. RESULTS: Compared with that of nonlaboring controls, serum interleukin-6 was significantly higher in patients with preterm premature rupture of membranes <24 hours before delivery with evidence of infection (17.2 vs 1.6 pg/ml, p < 0.0001). Patients with preterm premature rupture of membranes 24 to 48 hours before delivery who had infection had significantly higher interleukin-6 concentrations than did nonlaboring controls (3.6 vs 1.6 pg/ml, p = 0.006). There was no significant difference in interleukin-6 concentrations in nonlaboring controls compared with patients with preterm premature rupture of membranes when serum was obtained >48 hours before delivery (1.6 vs 1.6 pg/ml, p = 0.90). A serum interleukin-6 level greater than or equal to 8 pg/ml yielded a sensitivity of 81%, a specificity of 99%, a positive predictive value of 96%, and a negative predictive value of 95% for identifying intrauterine infection in patients with preterm premature rupture of membranes on the day of delivery. CONCLUSIONS: Maternal serum interleukin-6 concentrations are elevated in patients with preterm premature rupture of membranes with clinical or histologic chorioamnionitis.