title: 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.
abstract: OBJECTIVE
  Our purpose was to (1) determine the value of amniotic fluid interleukin-6 determination in the detection of microbial invasion of the amniotic cavity and (2) compare interleukin-6 to other rapid tests in the evaluation of preterm labor.
  
  
  METHODS
  Amniotic fluid interleukin-6 was determined quantitatively by enzyme-linked immunosorbent assay in 91 amniotic fluid specimens obtained by amniocentesis in 89 patients with preterm labor. Amniotic fluid cultures for aerobes, anaerobes, and mycoplasma species were performed. Receiver-operator characteristic curve analysis, logistic regression analysis, and Cox's proportional-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 limulus amebocyte lysate assay for prediction of a positive amniotic fluid culture, preterm delivery, clinical infection, and neonatal sepsis were calculated.
  
  
  RESULTS
  The prevalence of positive amniotic fluid cultures was 13% (12/89). The median interleukin-6 concentration in patients 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 specificity of an interleukin-6 level > or = 6.17 ng/ml was 75% and 79%, in contrast to that of glucose, < or = 12 mg/dl (83% and 86%) for a positive amniotic fluid culture and sensitivity (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 with a glucose level < or = 12 mg/dl. When all rapid tests and clinical parameters were considered simultaneously in the logistic 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 amniocentesis-to-delivery interval after clinical variables were controlled for (hazard ratio 3.01, p < 0.00001).
  
  
  CONCLUSIONS
  Amniotic fluid interleukin-6 determination may be a useful adjunct to our armamentarium of rapid tests to exclude infection and predict delivery in patients with preterm labor and intact membranes.
authors.affiliation: Fairfax Hospital, Falls Church, Virginia.
authors.forename: L L
authors.initials: LL
authors.lastname: Coultrip
authors.forename: J M
authors.initials: JM
authors.lastname: Lien
authors.forename: R
authors.initials: R
authors.lastname: Gomez
authors.forename: P
authors.initials: P
authors.lastname: Kapernick
authors.forename: A
authors.initials: A
authors.lastname: Khoury
authors.forename: J H
authors.initials: JH
authors.lastname: Grossman
mesh_terms: D000649:Amniocentesis; D000650:Amnion / Q000382:microbiology*; D000653:Amniotic Fluid / Q000737:chemistry* / Q000382:microbiology; D001419:Bacteria / Q000302:isolation & purification; D001424:Bacterial Infections / Q000175:diagnosis; D001431:Bacteriological Techniques; D002821:Chorioamnionitis / Q000175:diagnosis; D004797:Enzyme-Linked Immunosorbent Assay; D004950:Esterases / Q000097:blood; D005321:Extraembryonic Membranes; D005260:Female; D005947:Glucose / Q000032:analysis; D006801:Humans; D015850:Interleukin-6 / Q000032:analysis*; D007962:Leukocytes / Q000201:enzymology; D007752:Obstetric Labor, Premature / Q000378:metabolism / Q000382:microbiology*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis; D016016:Proportional Hazards Models; D012044:Regression Analysis; D012680:Sensitivity and Specificity
chemical_list: D015850:Interleukin-6; D004950:Esterases; D005947:Glucose