title: The natural history of bacterial vaginosis diagnosed by gram stain among women in Rakai, Uganda.
abstract: BACKGROUND
  Large datasets for investigating vaginal flora change at frequent, repeated intervals are limited and graphical methods for exploring such data are inadequate. We report 2-year weekly vaginal flora changes based on Gram stain using lasagna plots.
  
  
  METHODS
  Weekly vaginal flora patterns were evaluated among 211 sexually experienced women with ≥18 months of follow-up in Rakai, Uganda. Vaginal flora swabs were self-collected weekly and categorized by Nugent Gram stain criteria (0-3, normal; 4-6, intermediate; 7-10, bacterial vaginosis [BV]). Vaginal flora patterns were analyzed as the percentage of weekly observations with BV (longitudinal prevalence) and illustrated by lasagna plots. Characteristics of women were compared across tertiles of longitudinal prevalence of BV.
  
  
  RESULTS
  Ninety-five percent of women had at least 1 episode of BV over 2 years, with one-third of women spending more than half (52%-100%) of their time with BV. Vaginal pH >4.5 increased with increasing tertiles of longitudinal prevalence of BV (P < 0.001). Weekly fluctuation in vaginal flora states, as measured by a change in flora states from the before current visit, was highest in the middle (41.9%) compared with the lower (30.1%) and upper tertiles (27.8%, P < 0.001). HIV status and reported vaginal symptoms did not differ significantly across BV tertiles.
  
  
  CONCLUSIONS
  Women exhibited different patterns of vaginal flora changes over time, which could not be described by baseline behaviors. Lasagna plots aided in describing the natural history of BV within and across women and may be applied to future BV natural history studies.
authors: Department of Population, Family, and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. thomame@mail.nih.gov
authors: Marie E
authors: ME
authors: Thoma
authors: Ronald H
authors: RH
authors: Gray
authors: Noah
authors: N
authors: Kiwanuka
authors: Mei-Cheng
authors: MC
authors: Wang
authors: Nelson
authors: N
authors: Sewankambo
authors: Maria J
authors: MJ
authors: Wawer
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D005260:Female; D005840:Gentian Violet; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008137:Longitudinal Studies; D010619:Phenazines; D015995:Prevalence; D012725:Sexual Behavior; D014454:Uganda / Q000453:epidemiology; D014621:Vagina / Q000382:microbiology; D014626:Vaginal Smears; D016585:Vaginosis, Bacterial / Q000175:diagnosis* / Q000453:epidemiology* / Q000382:microbiology; D055815:Young Adult
chemical_list: C035863:Gram's stain; D010619:Phenazines; D005840:Gentian Violet