INCREASED INTERLEUKIN-6 CONCENTRATIONS IN CERVICAL SECRETIONS ARE ASSOCIATED WITH PRETERM DELIVERY

OBJECTIVE: This study sought to determine whether elevated concentrati ons of interleukin-6 in the cervical and vaginal secretions of patient s between 24 and 36 weeks' gestation predicted subsequent preterm deli very and/or identified those preterm deliveries associated with matern al infectious morbidity. STUDY DESIGN: A cohort study was untertaken w ith cervical and vaginal samples collected from 161 consenting patient s seen at 3- to 4-week intervals between 24 and 36 weeks. Levels of in terleukin-6 were measured by immunoassay. Demographic, obstetric, neon atal, and laboratory data-were analyzed by Fisher's exact test, Studen t t test, or Wilcoxon rank sum test, linear and multiple logistic regr ession, and receiver-operator characteristic curve analysis. RESULTS: There were 4.2-fold and 3.4-fold increases in maximal cervical and vag inal interleukin-6 concentrations, respectively, among patients with p reterm deliveries versus term deliveries. The receiver-operator charac teristics curve analysis indicated that a single cervical interleukin- 6 value > 250 pg/ml of sample buffer, present between 24 and 36 weeks' gestation, optimally identified patients with subsequent preterm deli veries versus term deliveries (sensitivity 50.0%, 95% confidence inter val 33.2% to 66.8%; specificity 85.0%, 95% confidence interval 78.8% t o 91.2%; positive predictive value 47.2%, 95% confidence interval 30.9 % to 63.5%; negative predictive value 86.4%, 95% confidence interval 8 0.4% to 92.4%). The optimal vaginal interleukin-6 cutoff value (>125 p g/ml) proved less sensitive (45.5%, 95% confidence interval 28.5% to 6 2.4%) but equally specific (86.6%, 95% confidence interval 80.7% to 92 .5%). Multiple logistic regression indicated that a cervical interleuk in-6 level > 250 pg/ml was an independent predictor of preterm deliver y (adjusted odds ratio 4.8, 95% confidence interval 1.7 to 14.3). Cerv ical interleukin-6 levels did not correlate with cervical change or ge stational age at sampling. Among patients delivered preterm there were no differences in the mean white blood cell count on admission or the prevalence of vaginal pathogens, alkaline vaginal pH, chorioamnioniti s, or endometritis among patients with cervical interleukin-6 values > 150 or > 250 pg/ml. CONCLUSIONS: Cervical interleukin-6 is a relative ly insensitive, although fairly specific discriminator of patients wit h subsequent preterm deliveries. Among patients delivered preterm, ele vated cervical interleukin-6 values are not apparently associated with maternal infectious morbidity.