Evaluation of rapid diagnostic tests in the detection of microbial invasion of the amniotic cavity.

OBJECTIVE: We sought to determine and compare the value of several rapid diagnostic tests in the detection of intraamniotic infection. STUDY
DESIGN: Gram stain, intraamniotic glucose level determination, leukocyte esterase assay, and the Limulus amebocyte lysate assay were performed on 144 amniotic fluid specimens retrieved by transabdominal amniocentesis in 136 patients with preterm premature rupture of the membranes or preterm labor. Diagnostic indices for a positive amniotic fluid culture and the development of clinical infection were calculated for each rapid test. Receiver-operator characteristic curves were generated to help select the optimal glucose level and combination of tests to detect intraamniotic infection.
RESULTS: The greatest sensitivity for predicting either a positive culture or subsequent clinical infection in preterm labor patients and in predicting clinical infection in patients with preterm premature rupture of the membranes was demonstrated by a low glucose level. The Gram stain provided the greatest positive predictive value in patients with preterm labor. Combining the Gram stain and measurement of intraamniotic glucose levels did not improve sensitivity above glucose alone or positive predictive value above Gram stain alone.
CONCLUSION: Leukocyte esterase determination and Limulus amebocyte lysate assay are insensitive indicators of intraamniotic infection. Selection of Gram stain or glucose level measurement alone or in combination as an appropriate screen for intraamniotic infection will depend on the clinicians' false-positive rate threshold.