Simplified gram stain interpretive method for diagnosis of bacterial vaginosis

Am J Obstet Gynecol. 1992 Jul;167(1):16-9. doi: 10.1016/s0002-9378(11)91617-2.


Objective: Two methods which only consider bacterial morphotypes and require counting various types of bacteria, for interpreting Gram stains of vaginal secretions for the purpose of diagnosing bacterial vaginosis were previously described. A new interpretative method, which combines clue cells with bacterial morphotypes as diagnostic markers, is offered.

Study design: One hundred twenty patients were tested with the new interpretative method and clinical criteria of bacterial vaginosis as the reference standard.

Results: The new method was found comparable to older methods when all were compared with clinical diagnostic methods. The sensitivity of the clue cell method was 86.1% and the specificity was 92.8%. The predictive value of a positive test was 83.7% for a population with a prevalence of bacterial vaginosis of 30%. The negative predictive value was 94.0%.

Conclusion: If clue cells are present and the nonlactobacilli morphotypes exceed lactobacilli morphotypes, bacterial vaginosis can be diagnosed without the need for exact bacterial counts.

MeSH terms

  • Adolescent
  • Adult
  • Bacteria / isolation & purification
  • Female
  • Gentian Violet*
  • Humans
  • Lactobacillus / isolation & purification
  • Phenazines*
  • Pregnancy
  • Pregnancy Complications, Infectious*
  • Staining and Labeling / methods*
  • Vaginosis, Bacterial / diagnosis*
  • Vaginosis, Bacterial / microbiology*
  • Vaginosis, Bacterial / pathology


  • Gram's stain
  • Phenazines
  • Gentian Violet