EVALUATING RAPID DIAGNOSTIC-TESTS OF INTRAAMNIOTIC INFECTION - GRAM STAIN, AMNIOTIC-FLUID GLUCOSE LEVEL, AND AMNIOTIC-FLUID TO SERUM GLUCOSE LEVEL RATIO

OBJECTIVE: The aim of the study was to compare the diagnostic utility of the Gram stain, the amniotic fluid glucose level, and the ratio of amniotic fluid glucose level to serum glucose level in detecting intra -amniotic infection. STUDY DESIGN: We conducted a prospective study of 127 patients with preterm labor and 26 patients with preterm prematur e rupture of the membranes (153 total). Ail patients underwent amnioce ntesis to diagnose intraamniotic infection. The diagnostic criterion f or intra-amniotic infection was a positive amniotic fluid culture resu lt. RESULTS: The Gram stain is 80% sensitive and 91% specific when a p ositive is considered the presence of white blood cells or bacteria. A mniotic fluid glucose level and the ratio of amniotic fluid glucose le vel to serum glucose level are significantly lower when amniotic fluid culture results are positive, but as diagnostic tests they are inferi or to the Gram stain. Logistic regression models that combine predicto rs yield superior accuracy with respect to individual tests. The most accurate combination was amniotic fluid glucose level and Gram stain w ith white blood cells or bacteria. Although the number of patients wit h preterm premature rupture of the membranes was small in this study ( n = 26), analysis of our data suggests that the diagnostic performance levels of these tests were similar when used in patients with preterm labor and intact membranes and in patients with premature rupture of the membranes. CONCLUSIONS: The amniotic fluid glucose level and the r atio of amniotic fluid to serum glucose level have equivalent diagnost ic utility and are inferior to the Gram stain. The combination of Gram stain with amniotic fluid glucose level is superior to any individual test.