What does the presence of clue cells on a wet prep indicate?

What Clue Cells on Wet Prep Mean

Clue cells on wet prep indicate bacterial vaginosis (BV), a condition where vaginal epithelial cells are covered with adherent bacteria, signaling disruption of normal vaginal flora. 1

Definition and Microscopic Appearance

• Clue cells are vaginal epithelial cells heavily coated with bacteria, giving them a stippled or granular appearance with obscured cell borders 1
• These bacterial-covered epithelial cells represent one of the four Amsel criteria used to diagnose bacterial vaginosis 1
• The bacteria adhering to these cells are predominantly Gardnerella vaginalis, anaerobes, and Mycoplasma hominis, which replace the normal Lactobacillus species 1

Clinical Significance

Clue cells alone do not definitively diagnose BV—the diagnosis requires at least 3 of 4 Amsel criteria:

• Homogeneous white discharge coating vaginal walls
• Vaginal pH >4.5
• Positive whiff test (fishy odor with KOH)
• Presence of clue cells on microscopy 1

Important Diagnostic Caveat

• Recent research reveals that not all "clue cells" are true clue cells—some are "pseudo clue cells" where epithelial cells are mechanically entrapped in bacterial masses rather than having bacteria directly adherent to the cell surface 2
• True clue cells with direct Gardnerella adherence occur in only 56% of samples initially diagnosed as having clue cells 2
• Using clue cells as the sole criterion for BV diagnosis has not been validated and is not recommended 1

What BV Means for Patient Outcomes

Non-Pregnant Women

• BV increases risk of pelvic inflammatory disease, endometritis, and post-surgical infections (endometrial biopsy, hysterectomy, IUD placement, abortion) 1
• Treatment with metronidazole substantially reduces post-abortion PID risk 1

Pregnant Women

• BV is associated with preterm delivery (RR 1.4-6.9), preterm premature rupture of membranes (RR 2.0-7.3), spontaneous abortion (RR 1.3-2.0), and preterm labor (RR 2.0-2.6) 1
• High-risk pregnant women (history of preterm delivery) may benefit from screening and treatment in the second trimester (13-24 weeks) 1
• Average-risk asymptomatic pregnant women should NOT be routinely screened, as treatment does not improve outcomes 1

Clinical Action Required

When clue cells are identified:

• Assess the other three Amsel criteria to confirm BV diagnosis 1
• Check vaginal pH (should be >4.5 in BV) 1
• Perform whiff test with KOH 1
• Evaluate discharge characteristics 1

Treatment is indicated for:

• All symptomatic women regardless of pregnancy status 1
• Asymptomatic high-risk pregnant women with history of preterm delivery 1
• Women undergoing invasive gynecologic procedures (abortion, hysterectomy) 1

Treatment is NOT indicated for:

• Asymptomatic average-risk pregnant women 1
• Asymptomatic non-pregnant women without planned procedures 1

Critical Pitfall to Avoid

• Up to 50% of women meeting clinical criteria for BV are asymptomatic—the presence of clue cells does not automatically require treatment unless the patient is symptomatic or falls into high-risk categories 1
• Partner treatment is not beneficial and does not prevent BV recurrence 1