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Literature reviews > Articles for review > Ramsey et al. Use of vaginal polymorphonuclear... |
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Coquantitation of epithelial cells with polymorphonuclear (PMN) cells may improve the reliability of PMN assessment on vaginal smear Gram stain preparations. Use of vaginal polymorphonuclear to epithelial cell ratios for the prediction of preterm birth. Question How well does a standardized technique using a polymorphonuclear cell to epithelial cell count ratio (PMN/EPI) improve the reliability of PMN assessment on vaginal Gram stain preparations and how well does this marker predict subsequent spontaneous preterm birth in asymptomatic women? Design This article describes a nested case-control study to assess the potential association between vaginal PMNs and risk for subsequent spontaneous preterm birth in a prospective longitudinal cohort of pregnant women using PMN count and PMN/EPI ratio determined from Gram stains of vaginal smears originally used for diagnosis of bacterial vaginosis (BV). Participants Asymptomatic women with intact membranes were prospectively enrolled between 20 and 25 weeks gestation. Eighty–three women with a spontaneous preterm birth at less than 35 weeks of gestation (cases) were compared with a control group of 108 randomly selected women who delivered at term (>37 weeks gestation). Description of Tests and Diagnostic Standard Swabs of the upper vagina and vaginal sidewalls were obtained for vaginal smear preparation, Gram stained, and evaluated for the presence of BV. PMN and vaginal epithelial cells were quantified on these slides using a standardized protocol. Five randomly selected fields were evaluated under oil immersion microscopy for the number of PMN and epithelial cells present in each field. PMN counts >100 were coded as 100; epithelial cell counts that were 0 were assigned a value of 1.Smudge cells were not included in the counts. PMN/EPI ratios were calculated for each evaluated slide field to control for intraslide variation in cellular density. Main Outcome Measures The mean PMN counts and mean PMN/EPI ratios and the PMN and PMN/EPI ratio 95th percentile cutoff values were compared between the cases and controls with and without logistic regression modeling to control for the presence of BV. Main Results The mean PMN count was higher in the cases (13 + 20 cells per field) than in the controls (10 + 14 cells per field) but this difference was not significant. The mean PMN/EPI ratio was significantly higher among the cases (3.4 + 6.0) than among the controls (1.8 + 2.4) (P = 0.01).PMN counts greater than the 95th percentile cutoff value (32.4 cells/field) were not associated with spontaneous preterm birth. PMN/EPI ratios greater than the 95th percentile cutoff value (7.0/field) were significantly associated with spontaneous preterm birth (odds ratio =3.8, P = 0.009).In a logistic regression model controlling for the presence of BV defined as a Nugent Gram stain score of >7, a PMN/EPI ratio greater than 7.0/field remained significantly associated with spontaneous preterm birth (odds ratio = 3.8, P = 0.01).The performances of the PMN count and of the PMN/EPI ratio for the prediction of women at risk for spontaneous preterm birth at less than 35 weeks gestation are shown in the table. Performance of vaginal smear PMN count and PMN/EPI ratio for the prediction of spontaneous preterm birth less than 35 weeks gestation
Authors' Conclusions The PMN/EPI ratio provided internal standardization of variation in slide cellular density and was significantly associated with subsequent spontaneous preterm birth at less than 35 weeks gestation. Use of a standardized approach for the PMN assessment on vaginal smear Gram stain preparations is needed as we further our understanding of the relationship of activation of the innate immune system with preterm labor and subsequent delivery. Source of funding: Grants from the National Institutes of Health/National Institute of Child Health and Human Development For correspondence: Patrick S. Ramsey, Division of Maternal-Fetal Medicine, Center for Research in Women's Health, University of Alabama at Birmingham, 619 19th Street South –458 Old Hillman Building, Birmingham, AL
35249-7333. |
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