clue cells in diagnosis of bacterial vaginosis

Last reviewed 07/2021

The detection of clue cells is a component of the Amsel criteria which is used in the diagnosis of bacterial vaginosis

  • clue cells (epithelial cells covered with small Gram-negative/Gram-variable rods) are detected by Gram staining of vaginal discharge by standard procedures and examination under oil immersion. Presence of clue cells in at least 20% of the oil immersion fields is considered positive by the Amsel criteria (1)
  • the presence of 'clue cells' has been found to be the most sensitive component of the Amstel criteria (2)

Bacterial vaginosis is conventionally diagnosed using Amsel criteria

  • the presence of any three of the following four criteria is considered to be consistent with the presence of bacterial vaginosis:
    • characteristic thin, homogenous vaginal discharge,
    • vaginal pH greater than 4.5,
    • release of a fishy amine odor on addition of 10% KOH (whiff test),
    • and demonstration of clue cells in more than 20% of the total cell population

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