THE VALUE OF AMNIOTIC-FLUID INTERLEUKIN-6 DETERMINATION IN PATIENTS WITH PRETERM LABOR AND INTACT MEMBRANES IN THE DETECTION OF MICROBIAL INVASION OF THE AMNIOTIC CAVITY

OBJECTIVES: Our purpose was to (1) determine the value of amniotic flu id interleukin-6 determination in the detection of microbial invasion of the amniotic cavity and (2) compare interleukin-6 to other rapid te sts in the evaluation of preterm labor. STUDY DESIGN: Amniotic fluid i nterleukin-6 was determined quantitatively by enzyme-linked immunosorb ent assay in 91 amniotic fluid specimens obtained by amniocentesis in 89 patients with preterm labor. Amniotic fluid cultures for aerobes, a naerobes, and mycoplasma species were performed. Receiver-operator cha racteristic curve analysis, logistic regression analysis, and Cox's pr oportional-hazards model were used to explore the relationship between several explanatory and outcome variables. Diagnostic index values of interleukin-6, glucose level, Gram stain, leukocyte esterase, and lim ulus amebocyte lysate assay for prediction of a positive amniotic flui d culture, preterm delivery, clinical infection, and neonatal sepsis w ere calculated. RESULTS: The prevalence of positive amniotic fluid cul tures was 13% (12/89). The median interleukin-6 concentration in patie nts with positive cultures was 241.8 ng/ml, in contrast to 0.291 ng/ml in patients with negative cultures (p. < 0.005). Sensitivity and spec ificity of an interleukin-6 level greater than or equal to 6.17 ng/ml was 75% and 79%, in contrast to that of glucose, less than or equal to 12 mg/dl (83% and 86%) for a positive amniotic fluid culture and sens itivity (p = 0.26, z test). All patients with an interleukin-6 level > 6.17 ng/ml were delivered preterm, in contrast to 85.2% of patients w ith a glucose level less than or equal to 12 mg/dl. When all rapid tes ts and clinical parameters were considered simultaneously in the logis tic model, only interleukin-6 maintained a significant relationship to preterm birth (odds ratio 35, p = 0.003). Cox's proportional analysis demonstrated a strong relationship between interleukin-6 and the amni ocentesis-to-delivery interval after clinical variables were controlle d for (hazard ratio 3.01, p < 0.00001). CONCLUSION: Amniotic fluid int erleukin-6 determination may be a useful adjunct to our armamentarium of rapid tests to exclude infection and predict delivery in patients w ith preterm labor and intact membranes.