What does the presence of clue cells in urine indicate?

Clue Cells in Urine Indicate Bacterial Vaginosis, Not Urinary Tract Infection

The presence of clue cells in urine samples is a diagnostic indicator of bacterial vaginosis (BV), not urinary tract infection, and requires treatment only when symptomatic. 1

What Are Clue Cells?

Clue cells are vaginal epithelial cells that are heavily coated with bacteria, giving them a stippled or granular appearance with indistinct borders when viewed under a microscope. They are specifically:

• Vaginal epithelial cells with adherent bacteria (primarily Gardnerella vaginalis)
• A key diagnostic criterion for bacterial vaginosis
• Visible in saline wet mount preparations
• Named "clue cells" because they provide a clue to the diagnosis of BV

Diagnostic Significance

Clue cells in urine samples are most likely the result of contamination from vaginal secretions during urine collection, as they originate from the vagina, not the urinary tract. Their presence indicates:

1. Bacterial Vaginosis: Clue cells are one of the four clinical criteria (Amsel criteria) used to diagnose BV 1:

   • Presence of clue cells on microscopic examination
   • Homogeneous, white, non-inflammatory discharge
   • Vaginal pH > 4.5
   • Fishy odor before or after adding 10% KOH (positive whiff test)

2. Not Urinary Tract Infection: Recent research shows that clue cells on vaginal wet preparation are not associated with UTIs or positive urine cultures 2. In fact, emergency physicians diagnosed significantly fewer women with UTIs when clue cells were present.

Clinical Implications

When clue cells are found in urine:

• Consider vaginal contamination: The presence of squamous cells (including clue cells) in urine samples is not a reliable indicator of bacterial contamination 3
• Evaluate for BV: If 20% or more of epithelial cells are clue cells, this is highly specific (94%) and sensitive (87%) for BV diagnosis 4
• Distinguish from other conditions: True clue cells with direct bacterial adherence to epithelial cells are unique to Gardnerella species and seen in only about 56% of BV cases; other cases may show "pseudo clue cells" where epithelial cells are mechanically entrapped in bacterial masses 5

Management Considerations

If clue cells are found in urine:

1. Assess for BV symptoms:

   • Vaginal discharge
   • Vaginal odor
   • Vulvar itching or irritation

2. Treatment indications:

   • Symptomatic patients: All women with symptomatic BV require treatment 1
   • Asymptomatic patients: Generally do not require treatment unless they are high-risk pregnant women or scheduled for invasive gynecological procedures 1

3. Special circumstances:

   • Pregnancy: BV during pregnancy is associated with adverse outcomes including premature rupture of membranes, preterm labor, and postpartum endometritis 1
   • Before invasive procedures: Consider treatment before procedures such as endometrial biopsy, hysterectomy, or abortion to reduce risk of post-procedure infection 1

Pitfalls to Avoid

• Don't assume UTI: The presence of clue cells does not indicate a UTI and should not lead to unnecessary antibiotic treatment for UTI 2
• Don't overlook mixed infections: Trichomoniasis can coexist with BV, though clue cells are not generally found in women with Trichomonas vaginalis alone 6
• Don't rely solely on clue cells: A complete assessment using all four Amsel criteria or Gram stain (Nugent score) provides more accurate diagnosis of BV 1
• Don't confuse with normal flora: True clue cells must show bacteria adherent to cell borders, not just bacteria near epithelial cells

Remember that the finding of clue cells in urine should prompt consideration of BV rather than UTI, and treatment should be directed accordingly when symptoms are present.