Reliability of diagnosing bacterial vaginosis is improved by a standardized method of gram stain interpretation

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Abstract

The purpose of the study was to examine intercenter variability in the interpretation of Gram-stained vaginal smears from pregnant women. The intercenter reliability of individual morphotypes identified on the vaginal smear was evaluated by comparing them with those obtained at a standard center. A new scoring system that uses the most reliable morphotypes from the vaginal smear was proposed for diagnosing bacterial vaginosis. This scoring system was compared with the Spiegel criteria for diagnosing bacterial vaginosis. The scoring system (0 to 10) was described as a weighted combination of the following morphotypes: lactobacilli, Gardnerella vaginalis or bacteroides (small gram-variable rods or gram-negative rods), and curved gram-variable rods. By using the Spearman rank correlation to determine intercenter variability, gram-positive cocci had poor agreement (0.23); lactobacilli (0.65), G. vaginalis (0.69), and bacteroides (0.57) had moderate agreement; and small (0.74) and curved (0.85) gram-variable rods had good agreement. The reliability of the 0 to 10 scoring system was maximized by not using gram-positive cocci, combining G. vaginalis and bacteroides morphotypes, and weighting more heavily curved gram-variable rods. For comparison with the Spiegel criteria, a score of 7 or higher was considered indicative of bacterial vaginosis. The standardized score had improved intercenter reliability (r = 0.82) compared with the Spiegel criteria (r = 0.61). The standardized score also facilitates future research concerning bacterial vaginosis because it provides gradations of the disturbance of vaginal flora which may be associated with different levels of risk for pregnancy complications.

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A case-control study of chorioamnionic infection and histologic chorioamnionitis in prematurity.

Susan L. Hillier, J Martius, N Kiviat … (1988)

To study the role of infection in prematurity, we studied the demographic and obstetrical characteristics, chorioamnionic cultures, and placental histologic features of women who delivered prematurely and compared these findings with those in women who delivered at term. Microorganisms were isolated from the area between the chorion and the amnion (chorioamnion) in 23 of 38 placentas (61 percent) from women with preterm labor who delivered before 37 weeks' gestation and in 12 (21 percent) of 56 placentas from women without preterm labor who delivered at term (odds ratio, 5.6; 95 percent confidence interval, 2.1 to 15.6). The most frequent isolates from the placentas of those whose infants were delivered prematurely were Ureaplasma urealyticum (47 percent) and Gardnerella vaginalis (26 percent). The recovery of any organism from the chorioamnion was strongly associated with histologic chorioamnionitis (odds ratio, 7.2; 95 percent confidence interval, 2.7 to 19.5) and with bacterial vaginosis (odds ratio, 3.2; 95 percent confidence interval, 1.1 to 6.6). When multiple logistic regression was used to control for demographic and obstetrical variables, premature delivery was still related to the recovery of organisms from the chorioamnion (odds ratio, 3.8; 95 percent confidence interval, 1.5 to 9.9) and with chorioamnionitis (odds ratio, 5.0; 95 percent confidence interval, 1.6 to 15.3). The proportion of placentas with evidence of infection was highest among those who delivered at the lowest gestational age. We conclude that infection of the chorioamnion is strongly related to histologic chorioamnionitis and may be a cause of premature birth.