Amniotic fluid interleukin-6 levels correlate with histologic chorioamnionitis and amniotic fluid cultures in patients in premature labor with intact membranes.

Our purpose was (1) to determine the frequency of intraamniotic and extraamniotic intrauterine infection in patients with premature labor and intact membranes and (2) to determine if intrauterine infection is associated with elevated amniotic fluid interleukin-6 levels. Amniocentesis was performed on 57 patients in preterm labor and 201 controls at various gestational ages without labor and at term with labor. The amniotic fluid was evaluated with gram stain, cultures, and an enzyme-linked immunosorbent assay specific for interleukin-6. Placentas from study patients (n = 52) and term controls (n = 120) were analyzed. The frequency of positive amniotic fluid cultures (intraamniotic intrauterine infection) was 10 of 57 (18%) in the preterm labor group and zero of 201 for controls. Histologic chorioamnionitis (extraamniotic intrauterine infection) was present in 21 of 24 (88%) of patients in preterm labor that failed tocolysis and 28 of 120 (23%) of term laboring controls. An amniotic fluid interleukin-6 level of > or = 600 pg/ml was 100% sensitive and 89% specific (positive predictive value 85%, negative predictive value 100%) for the identification of intrauterine infection. Interleukin-6 is a sensitive and specific marker for the identification of both intraamniotic and extraamniotic intrauterine infection in patients in preterm labor with intact membranes.