The negative predictive value of cervical interleukin-6 for the risk assessment of preterm birth

Abstract

Objective: To determine the potential clinical use of cervical interleukin-6 (IL-6) as a negative predictor of preterm birth in symptomatic women.Study design: Observational prospective study carried out in a tertiary hospital.Patients and methods: We studied 100 singleton pregnant women with threatened preterm delivery and intact membranes, between 24 and 34 weeks, recruited during the period 2006–2008. A cervical swab for IL-6 detection was taken and a transvaginal ultrasound scan was performed for measuring the cervical length.Results: Five women delivered within 2 d and six women within 7 d. A high cervical IL-6 concentration was found in these women. The area under the ROC curve for cervical IL-6 was 0.97 for deliveries within 2 d after the test, and 0.85 for deliveries within 7 d. The optimal cut-off point was a cervical IL-6 concentration of 210 pg/ml. The negative predictive value (NPV) was 100% for deliveries within 2 d, and 98.5% for deliveries within 7 d (when considering a prevalence of preterm birth of 8%). Cervical IL-6 and sonographic measurement of cervical length showed similar NPV.Conclusion: A low-cervical IL-6 concentration can accurately identify symptomatic women with a very low chance to progress to preterm birth within 2–7 d.