The value of chorioamniotic plate smears in predicting intraamniotic infection

Direct cytobacteriological investigation of the chorioamniotic plate, the placental smear test (PST), was used for rapid diagnosis of intraamniotic infection. Diagnostic value and limitations of the test are reviewed in a retrospective study of 300 consecutive cases, including 53 term deliveries with and without clinical evidence of infection, 105 premature deliveries, 103 second trimester spontaneous abortions, and 39 stillbirths. Evaluation of the PST and comparisons with paacental cultures were made using histologic chorioamnionitis as reference standard. The diagnostic indices of PST were found to be: sensitivity 54.8%, specificity 79.5%, positive predictive value 62.4%, and negative predictive value 73.9%. The diagnostic indices for the placental cultures were: sensitivity 58.9%, specificity 78.6%, positive predictive value 68.2%, and negative predictive value 73.0%. There were no differences in the diagnostic value of the two tests. However, the PST permits diagnosis of amniotic infection escaping detection by culture owing to antibiotics being given before the onset of labor. The PST seems to be more valuable than culture in the vaginal delivery group.