What is the next step in managing a 24-year-old female patient with pink vaginal discharge, negative tests for gonorrhea (Neisseria gonorrhoeae) and chlamydia (Chlamydia trachomatis), negative trichomoniasis (Trichomonas vaginalis), and a normal Pap (Papanicolaou) smear?

Management of Pink Vaginal Discharge with Negative STI Testing

The next step is to perform vaginal pH testing and wet mount microscopy to evaluate for bacterial vaginosis, vulvovaginal candidiasis, or other non-sexually transmitted causes of discharge. 1

Diagnostic Approach

With negative testing for gonorrhea, chlamydia, and trichomoniasis, the differential diagnosis shifts to non-sexually transmitted causes of vaginal discharge:

Immediate Bedside Testing Required

• Measure vaginal pH using narrow-range pH paper—an elevated pH >4.5 suggests bacterial vaginosis or residual concern for trichomoniasis (though already tested negative) 1
• Perform wet mount microscopy by diluting vaginal discharge in 1-2 drops of 0.9% normal saline on one slide and 10% KOH on a second slide 1
• Perform the "whiff test" by adding 10% KOH to the discharge—a fishy amine odor indicates bacterial vaginosis or trichomoniasis 1

What to Look For on Microscopy

• Saline wet mount: Look for clue cells (vaginal epithelial cells with adherent bacteria obscuring borders), which indicate bacterial vaginosis 1
• KOH preparation: Look for yeast, pseudohyphae, or budding forms indicating vulvovaginal candidiasis 1
• White blood cells: Presence of WBCs on saline microscopy may suggest cervicitis, though this is less likely given negative gonorrhea/chlamydia testing 1

Most Likely Diagnoses

Bacterial Vaginosis (Most Common)

Bacterial vaginosis is the most prevalent cause of vaginal discharge or malodor in reproductive-age women. 1 The pink color may represent blood-tinged discharge mixed with the characteristic thin, white discharge of BV.

Diagnostic criteria (need 3 of 4): 1

• Homogeneous, white, noninflammatory discharge adhering to vaginal walls
• Clue cells on microscopy
• Vaginal pH >4.5
• Positive whiff test (fishy odor with KOH)

Treatment if BV confirmed: Metronidazole 500 mg orally twice daily for 7 days 2

Vulvovaginal Candidiasis

Candidiasis typically presents with pruritus, white discharge, and vulvar erythema with a normal pH ≤4.5. 1 The pink discharge makes this less likely but not impossible if there is associated irritation causing minor bleeding.

Treatment if candidiasis confirmed: Topical azole therapy (e.g., clotrimazole 1% cream 5g intravaginally for 7-14 days or miconazole 2% cream for 7 days) 1

Critical Pitfalls to Avoid

Don't Miss Cervicitis

Even with negative gonorrhea/chlamydia testing, examine the cervix for mucopurulent discharge—the presence of yellow endocervical exudate or increased polymorphonuclear leukocytes suggests mucopurulent cervicitis. 1 While most MPC is caused by chlamydia or gonorrhea, other organisms can be responsible. 1

Consider Timing of Testing

False-negative results can occur if testing was performed too early after exposure. 1 If there is high clinical suspicion for STI despite negative testing, consider:

• Repeat testing in 2 weeks 1
• The pink discharge could represent post-coital bleeding or cervical friability from undetected cervicitis

Trichomoniasis Detection Limitations

Culture for Trichomonas vaginalis is more sensitive than wet mount microscopy alone. 1 If the initial test was only wet mount or rapid antigen testing, consider sending a culture if clinical suspicion remains high. 3, 4 Pap smears can occasionally detect trichomonas missed by other methods, though this is not a primary diagnostic tool. 3, 4

Alternative Considerations

Physiologic or Hormonal Causes

• Pink discharge may represent normal mid-cycle spotting (ovulation bleeding) mixed with physiologic discharge in a 24-year-old woman 5, 6
• Approximately 10-20% of women normally harbor Candida species without symptoms 1

Mechanical or Chemical Irritation

Vulvar inflammation without identified pathogens suggests mechanical or chemical irritation. 1 Ask about:

• New soaps, detergents, or feminine hygiene products
• Recent sexual activity or use of lubricants
• Douching practices

Treatment Algorithm

If wet mount and pH testing reveal bacterial vaginosis: Treat with metronidazole 500 mg orally twice daily for 7 days 2

If yeast is identified: Treat with topical azole antifungal for 7 days 1

If testing is negative but symptoms persist: Consider empiric treatment for bacterial vaginosis given its high prevalence and the fact that 50% of women with BV are asymptomatic 1, 2

If no pathogen is identified and symptoms resolve: Reassure the patient that this may represent physiologic variation 5

Follow-Up Strategy

• No follow-up needed if symptoms resolve with treatment 2
• Reassess if symptoms persist beyond 2 weeks or recur within 2 months 1, 7
• Consider repeat STI testing if new symptoms develop or if there was recent high-risk exposure 1