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Diagnosis of intra-amniotic infection: the acridine orange stain
R Romero1, M Emamian, R Quintero
1Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, Connecticut 06510.
Abstract:
The rapid diagnosis of intra-amniotic infection in patients with premature rupture of the membranes (PROM) and preterm labor is of utmost importance. The Gram's stain examination of amniotic fluid can only detect half of these infections. The acridine orange (AO) stain has been claimed to be superior to the Gram's stain in the detection of bacteria in biologic fluids. Therefore, we undertook the present study to examine the value of AO in the detection of bacteria in amniotic fluid. One hundred and thirty-eight patients with a culture-documented prevalence of intra-amniotic infection of 23.2% were studied. The diagnostic indices of the AO were: sensitivity, 43.8%, specificity, 97.2%, positive predictive value, 82.8%, and negative predictive value, 85.1%; the diagnostic indices for the Gram's stain were: sensitivity, 46.8%, specificity, 98.1%, positive predictive value, 88.2%, and negative predictive value, 85.9%. There was no difference in the diagnostic values of the tests. The agreement between the two techniques was substantial, as indicated by a kappa index of 0.72 (SE = 0.17, p less than 0.001). The AO offered no significant advantage over the Gram's stain examination of amniotic fluid in the detection of intra-amniotic infection. However, the AO stain was able to identify mycoplasma infections that escaped detection by the Gram's stain. Therefore, the AO is presently the only microscopic technique capable of detecting mycoplasma in amniotic fluid.
Insights
Acridine orange (AO) stain and Gram
Area of Science:
- Obstetrics and Gynecology
- Medical Microbiology
- Diagnostic Pathology
Background:
- Intra-amniotic infection diagnosis is critical for patients with premature rupture of membranes (PROM) and preterm labor.
- Gram's stain has limited sensitivity for detecting bacteria in amniotic fluid.
- Acridine orange (AO) stain is proposed as a more sensitive alternative for bacterial detection.
Purpose of the Study:
- To evaluate the diagnostic value of acridine orange (AO) stain compared to Gram's stain for detecting intra-amniotic infection.
- To assess the utility of AO stain in identifying specific microorganisms like Mycoplasma.
Main Methods:
- A study involving 138 patients with culture-documented intra-amniotic infection.
- Comparative analysis of diagnostic indices (sensitivity, specificity, predictive values) for AO stain and Gram's stain.
- Assessment of agreement between the two staining techniques using the kappa index.
Main Results:
- Both AO stain and Gram's stain demonstrated comparable diagnostic values for overall intra-amniotic infection detection.
- No significant difference in sensitivity, specificity, or predictive values was observed between the two methods.
- AO stain uniquely identified Mycoplasma infections, which were missed by Gram's stain.
Conclusions:
- Acridine orange (AO) stain offers no significant advantage over Gram's stain for routine amniotic fluid bacterial detection in intra-amniotic infection.
- AO stain is the only microscopic method capable of detecting Mycoplasma in amniotic fluid.
- The study highlights the specific utility of AO stain for Mycoplasma identification.