What are the typical diagnostic tests for trichomoniasis?

Diagnostic Testing for Trichomoniasis

Nucleic acid amplification testing (NAAT) is the most appropriate diagnostic test for trichomoniasis, offering superior sensitivity compared to all other methods and accepting multiple specimen types including vaginal swabs, endocervical swabs, urine, and liquid-based cytology specimens. 1

Primary Diagnostic Approach

First-Line Testing: NAAT

• NAAT should be the preferred diagnostic method when available, as it provides the highest sensitivity and does not require viable organisms for detection 1, 2
• Multiple specimen types can be used: vaginal swabs, endocervical swabs, urine, liquid-based cytology specimens, and even urethral, rectal, or pharyngeal swabs 1
• Specimens remain stable at room temperature for 7 days (or per manufacturer's recommendations), allowing flexibility in transport 1
• The FDA has cleared NAAT testing (such as APTIMA Trichomonas vaginalis test) for both screening and diagnosis in women 1

Point-of-Care Testing Options

Saline Wet Mount

• Requires examination within 30 minutes (optimal) to 2 hours of collection, as live organisms must be visualized 1, 2
• Sensitivity is poor at only 40-80%, meaning it misses 20-60% of infections 1, 2
• The specimen should be collected from vaginal discharge and submitted in saline 1
• Despite low sensitivity, wet mount remains useful when a microscope is immediately available and positive results allow immediate treatment 2

Rapid Antigen Testing

• Does not require live organisms for optimal performance 1
• Sensitivity ranges from 62% to 95% compared to culture and NAAT, with best results in symptomatic patients 1
• Specimens can be submitted in transport swab or saline and remain stable at room temperature for 24 hours 1
• The OSOM Trichomonas Rapid Test is one commercially available option 1

Alternative Diagnostic Methods

Culture

• The InPouch TV culture system allows both immediate smear review by wet mount and subsequent culture 1
• Sensitivity is approximately 70% compared to NAAT methods 1
• Specimens should be placed directly into the InPouch TV Culture system and remain stable at room temperature for 48 hours 1
• Culture is not widely available and has been largely superseded by NAAT 1

DNA Hybridization Probe

• The Affirm VP III Assay detects Trichomonas vaginalis but has lower sensitivity than NAAT 1
• Does not rely on viable organisms for optimal test performance 1
• FDA-cleared for vaginal specimens from symptomatic female patients only 1
• Specimens remain stable at room temperature for 7 days 1

Clinical Context and Supporting Findings

Key Clinical Indicators

• Vaginal pH >4.5 is a key finding that distinguishes trichomoniasis from candidiasis 2
• Up to 50% of trichomoniasis infections are asymptomatic, so absence of symptoms does not exclude infection 2
• The "strawberry cervix" (punctate red lesions) is specific but not always present 2

Testing Algorithm

• If microscope is immediately available: Perform wet mount and measure vaginal pH; if positive, treat immediately 2
• If wet mount is negative but clinical suspicion is high (pH >4.5, symptoms present): Send NAAT, culture, or rapid antigen test 2
• For screening asymptomatic high-risk populations: Use NAAT, which is more sensitive than wet mount 2

Critical Pitfalls to Avoid

• Never rely solely on wet mount due to its poor sensitivity of 40-80%; negative wet mount does not exclude trichomoniasis 1, 2
• Do not delay wet mount examination beyond 2 hours, as organisms lose motility and become undetectable 1, 2
• Avoid using urine-based detection exclusively in women, as sensitivity is only 64% compared to 89% for vaginal specimens 3
• Always treat sexual partners simultaneously to prevent reinfection, even if their testing is negative 4
• Confirm diagnosis with appropriate laboratory procedures (wet smears and/or cultures) before treatment, as required by FDA labeling for metronidazole 4