Amniotic fluid Gram stain and culture have been utilized as laboratory tests of microbial
invasion of the amniotic cavity. The Gram stain of amniotic fluid has a low sensitivity in the
detection of clinical infection or microbial invasion of the amniotic cavity, and amniotic fluid
culture results are not immediately available for management decisions. Glucose
concentration is used to diagnose infection in other sites such as cerebrospinal fluid.
Objective: The purpose of this study was to evaluate the usefulness
of amniotic fluid glucose concentration in detecting microbial invasion of the amniotic
cavity associated with preterm labor and preterm premature rupture of membranes.
Methods: Amniocentesis was performed in 60 women with preterm labor
and/or preterm premature rupture of membranes. Gram stain and culture for Mycoplasma hominis,
Ureaplasma urealyticum, aerobic, and anaerobic bacteria were performed. Subjects
were studied prospectively for the development of positive amniotic fluid cultures and the
development of clinical chorioamnionitis.
Results: The diagnosis of clinical chorioamnionitis was made in
25% (15/60) of women entered into the study. Low amniotic fluid glucose concentration
Was considered < 15 mg/dl. The sensitivity, specificity, and positive predictive value
of low amniotic, fluid glucose concentration to predict clinical chorioamnionitis were 73.3%,
88.1%, and 68.8% respectively, while positive amniotic fluid culture, hada sensitivity of
43.8%, specificity of 79.5%, and positive predictive value of 43.8%.
Conclusions: Amniotic fluid glucose concentration was more sensitive
in predicting chorioamnionitis than either Gram stain or culture. Amniotic fluid glucose
concentration was better in predicting clinical chorioamnionitis than predicting positive
amniotic fluid culture results. Gestational age-dependent normal ranges and pathologic
conditions that may alter amniotic fluid glucose concentrations should be considered
when interpreting amniotic fluid glucose values to diagnose microbial invasion of the