What is the differential diagnosis and treatment approach for vaginal itching and burning?

Differential Diagnosis of Vaginal Itching and Burning

The three most common infectious causes—bacterial vaginosis (40-50%), vulvovaginal candidiasis (20-25%), and trichomoniasis (15-20%)—account for 75-90% of cases when a cause is identified, with noninfectious causes (atrophic, irritant, allergic, inflammatory vaginitis) comprising 5-10%. 1, 2

Diagnostic Algorithm

Step 1: Measure Vaginal pH

• pH ≤4.5 suggests vulvovaginal candidiasis 3, 4
• pH >4.5 indicates bacterial vaginosis or trichomoniasis 3, 4
• Apply narrow-range pH paper directly to vaginal secretions 3

Step 2: Perform Microscopy Based on pH

For pH ≤4.5 (Suspected Candidiasis):

• Examine KOH preparation for yeast or pseudohyphae 3, 1
• If microscopy negative but symptoms present, consider DNA probe testing or culture (especially for recurrent cases to identify non-albicans species like Candida glabrata or Candida tropicalis) 1, 5

For pH >4.5 (Suspected BV or Trichomoniasis):

• Perform saline wet mount to identify:
  • Clue cells (epithelial cells studded with bacteria) = bacterial vaginosis 3, 4
  • Motile trichomonads = trichomoniasis 3, 4
• Whiff test: fishy odor after KOH application confirms BV or trichomoniasis 3, 2
• For trichomoniasis, nucleic acid amplification testing is superior to microscopy (which has high false-negative rates) 1, 5

Step 3: Consider Noninfectious Causes if Testing Negative

• Atrophic vaginitis: Estrogen deficiency causing vaginal dryness, itching, irritation, dyspareunia; normal pH may be elevated; responds to topical or systemic estrogen 2, 5
• Irritant/allergic contact vaginitis: History of new soaps, douches, spermicides, latex exposure; remove offending agent 2
• Desquamative inflammatory vaginitis: Consider in treatment-refractory cases; may respond to topical clindamycin and steroids 1, 6
• Seminal fluid hypersensitivity: Symptoms begin within seconds to minutes after ejaculation; prevented by condom use; requires skin testing for confirmation 7

Treatment Protocols

Bacterial Vaginosis

• First-line: Metronidazole 500 mg orally twice daily for 7 days (95% cure rate) 3
• Alternative: Clindamycin cream intravaginally 3
• Do NOT treat male partners—this does not prevent recurrence 3
• Recurrence is common (50-80% within one year) but does not change initial management 3

Vulvovaginal Candidiasis

• Uncomplicated: Fluconazole 150 mg orally as single dose (55% therapeutic cure rate) 3, 8
• Alternative: Topical azoles (equally effective) 1, 5
• Pregnant women: Use only 7-day topical azole treatments (NOT oral fluconazole) 3, 9
• Recurrent/complicated: Fluconazole 150 mg weekly for 6 months 3
• Do NOT treat partners 3

Trichomoniasis

• Metronidazole 2 grams orally as single dose (90-95% cure rate) 3, 1
• Alternative: Tinidazole 2 grams orally as single dose 10
• MUST treat sexual partners simultaneously to prevent reinfection 3, 1
• For treatment failures, use 7-day metronidazole course 6

Atrophic Vaginitis

• Topical or systemic estrogen therapy 2, 5

Critical Pitfalls to Avoid

• Do not assume thick white discharge always means candidiasis—only 10-20% of cases with these symptoms are actually yeast infections; pH and microscopy are essential 1, 5
• Do not rely solely on wet mount for trichomoniasis—microscopy has high false-negative rates; use nucleic acid amplification testing in symptomatic or high-risk women 1, 5
• Do not treat partners for BV or candidiasis—only trichomoniasis requires partner treatment 3
• Do not use oral fluconazole in pregnancy—teratogenic risk; use only topical azoles for 7 days 3, 8
• Do not mistake cervical ectropion for infection in adolescents—this is a normal developmental finding 4
• Reconsider diagnosis if treatment fails—evaluate for desquamative inflammatory vaginitis, genitourinary syndrome of menopause, vulvodynia, or non-albicans Candida species 6

Special Populations

• HIV-infected women receive identical treatment regimens as non-HIV-infected women for all three conditions 3
• Pregnant women require 7-day topical treatments only for BV and candidiasis 3

Follow-Up

• Return only if symptoms persist or recur within 2 months 3
• Routine test-of-cure is NOT necessary if symptoms resolve 3