Vaginal pH and parabasal cells in postmenopausal women

Objective: To determine the vaginal pH level that correlates with elevated parabasal cells in vaginal smears Methods: Postmenopausal women presenting to a gynecology office for routine annual and incontinence examinations were studied prospectively. Women were excluded if they had vaginal infections or pelvic organ prolapses past the hymen. pH was measured and cytology smears made from the midvagina. A pathologist who was not aware of pH results evaluated the smears, Spearman rho was used to correlate pH and percentage of parabasal cells. Logistic regression was used to analyze the relationship between pH and increased parabasal cells in vaginal smears. Predictive values were used to select a pH level as a cutoff point to predict increased parabasal cells. Results: Seventy-four women were enrolled and 70 completed the study. The correlation coefficient between pH and percentage of parabasal cells was 0.6 (P < .001). Logistic regression showed association of pH with 20% or more parabasal cells (P <.001), Positive and negative predictive values for pH level above 6.0 as a predictor of 20% or more parabasal cells were 96.3% and 87.5%, respectively. The prevalence of elevated parabasal cells was 22.9%. Conclusion: Vaginal pH above 6.0 correlates with high levels of parabasal cells (20% or more) from the midvagina. (C) 1999 by The American College of Obstetricians and Gynecologists.