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14: Amniotic fluid glucose and interleukin-6 as independent markers of intraamniotic infection in preterm labor

      Objective

      Intraamniotic infection (IAI) is a common cause of preterm labor (PTL) at early gestational age (GA). IAI is associated with short latency to delivery, resulting in a high risk of perinatal morbidity and mortality (PM&M). Most IAI is subclinical, so prompt diagnosis requires analysis of amniotic fluid (AF). AF markers for IAI that are potentially available rapidly include low glucose, high interleukin-6 (IL6), high white cell count, and positive gram stain. Previous studies have shown that glucose and IL6 have the best sensitivity and specificity. We sought to determine whether AF glucose and IL6 are independent markers of IAI.

      Study Design

      This is a secondary analysis of a multicenter, prospective observational study. Women with preterm labor, 22-36 wks GA, singleton pregnancy, intact membranes underwent amniocentesis for culture, 16S rDNA by PCR, AF glucose, and AF IL6. Microbial invasion of amniotic cavity (MIAC) was defined by positive culture or 16S rDNA. Low AF glucose was defined as less than 20 mg/dL. High AF IL6 was defined as 11.3 ng/mL or more. Low glucose and high IL6 were examined as predictors of MIAC, latency to delivery less than 3 days, and composite PM&M in univariable analyses and in logistic regression adjusting for GA at presentation and other variables.

      Results

      Among 298 women with PTL, MIAC was present in 29 (10%). Both low glucose and high IL6 were predictive of MIAC in univariable analyses (odds ratio 35.2 [95%CI 11-112], 40.6 [13-123]; sensitivity 89%, 86%; specificity 88%, 87%; positive likelihood ratio 7.5 [5.3-10.7], 6.5 [4.6-9.1], respectively), with similar areas under ROC curve (0.92, 0.89, P=0.41). Logistic regression analyses are summarized in Table, showing that both glucose and IL6 are strong, independent predictors of MIAC, short latency, and composite PM&M. Latency to delivery is plotted in Figure, showing that either marker alone is strongly associated with short latency and that the combination of both markers was associated with the shortest latency.

      Conclusion

      AF glucose and IL6 are independent predictors of MIAC, short latency, and composite PM&M in women with PTL. When using these tests to predict IAI, sensitivity will be maximized by using both tests together, considering either low glucose, high IL6, or both as markers of MIAC.
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