In Vitro Bacterial Contamination of Amniotic Fluid: Effects on Fluorescence Polarization Lung Maturity Testing

OBJECTIVE We sought to determine the effect of bacteria on fluorescence polarization (FPOL) testing of amniotic fluid. METHODS Fusobacterium necrophorum and Escherichia coli were inoculated at concentrations of 10(3) and 10(6)/ml in amniotic-fluid specimens from 4 patients with no clinical or laboratory evidence of infection. The FPOL results were obtained at inoculation and again at 24 h of incubation. The results were compared using analysis of variance (ANOVA). RESULTS The FPOL results from inoculated specimens were all within 2% of the uninoculated controls. The specimens incubated with bacteria showed a < 1-19% variation when compared with the time-zero uninoculated controls. However, uninoculated controls incubated for 24 h exhibited a 2-12% variation when compared with the time-zero controls, suggesting that the variation present was not secondary to the bacterial co-incubation. CONCLUSIONS In vitro, neither bacterial inoculation nor prolonged co-incubation influences FPOL results beyond the effect of incubation alone. FPOL appears to be an appropriate test to assess fetal lung maturity in patients in whom intraamniotic infection is a concern.