A comparative study of the diagnostic performance of amniotic fluid glucose, white blood cell count, interleukin-6, and gram stain in the detection of microbial invasion in patients with preterm premature rupture of membranes.

OBJECTIVE

Our aim was to compare the value of amniotic fluid tests for the detection of microbial invasion of the amniotic cavity and in the prediction of the amniocentesis-to-delivery interval and neonatal complications in patients with preterm premature rupture of membranes.

STUDY DESIGN

Amniotic fluid was obtained by transabdominal amniocentesis from 110 consecutive patients with preterm premature rupture of membranes. Fluid was cultured for aerobic and anaerobic bacteria, as well as mycoplasmas. Amniotic fluid analysis included a Gram stain examination, white blood cell count, and glucose and interleukin-6 determinations. Logistic regression and survival techniques (proportional hazards model) were used for statistical analysis.

RESULTS

(1) The prevalence of positive amniotic fluid cultures in patients with preterm premature rupture of membranes was 38% (42/110); (2) patients with microbial invasion had a shorter amniocentesis-to-delivery interval and a higher neonatal complication rate than patients with negative cultures; (3) the most sensitive test for the detection of microbial invasion of the amniotic cavity was amniotic fluid interleukin-6 determinations (cutoff 7.9 ng/ml) (sensitivity: for IL-6 80.9%; for white blood cell count 57.1%; for glucose 57.1%; for Gram stain 23.8%; p < 0.05 for all comparisons); (4) the most specific test for the detection of microbial invasion was the Gram stain of amniotic fluid (specificity: for Gram stain 98.5%; for white blood cell count 77.9%; for interleukin-6 75%; for glucose 73.5%; p < 0.01 for all); (5) of all amniotic fluid tests, interleukin-6 determination was the only test that had significant clinical value in the prediction of the amniocentesis-to-delivery interval and neonatal complications.

CONCLUSION

Interleukin-6 concentrations in amniotic fluid are a better predictor of microbial invasion of the amniotic cavity, amniocentesis-to-delivery interval and neonatal complications than the amniotic fluid Gram stain, glucose, or white blood cell count in patients with preterm premature rupture of membranes.