What is the assessment and diagnosis for Trichomonas vaginalis?

Assessment and Diagnosis of Trichomonas Vaginalis

Nucleic acid amplification testing (NAAT) is the preferred diagnostic method for Trichomonas vaginalis, offering superior sensitivity (>80%) compared to all other methods and accepting multiple specimen types including vaginal swabs, endocervical swabs, and urine. 1, 2

Clinical Assessment

Symptomatic Presentation

• Vaginal discharge (with or without characteristic odor) is the most common presenting symptom in women 2
• Pruritus or vulvar irritation frequently accompanies the discharge 2
• Elevated vaginal pH >4.5 is a critical distinguishing feature that differentiates trichomoniasis from candidiasis 2, 3
• "Strawberry cervix" (punctate red lesions on the cervix) is highly specific but present in only a minority of cases 2
• Cervical friability and hyperemia may be observed on speculum examination 2

Asymptomatic Infections

• Up to 50% of infections are asymptomatic, making the absence of symptoms unreliable for excluding infection 2
• Screen asymptomatic women with multiple sexual partners or other STI risk factors 2

High-Risk Populations Requiring Screening

• Women with new or multiple sexual partners 1
• Patients with history of sexually transmitted infections 1
• HIV-infected women (annual screening recommended) 1
• Pregnant women to prevent adverse pregnancy outcomes 1
• Patients with suspected pelvic inflammatory disease 1

Diagnostic Testing Algorithm

First-Line Testing: NAAT (Preferred Method)

NAAT should be the primary diagnostic test when available due to its superior sensitivity and specificity. 1, 2

• Sensitivity: >80% compared to 40-80% for wet mount 1, 2
• Acceptable specimen types: vaginal swabs (provider or self-collected), endocervical swabs, urine, liquid-based cytology specimens, urethral, rectal, or pharyngeal swabs 1
• Specimen stability: Room temperature for 7 days (or per manufacturer's recommendation) 1
• FDA-cleared tests: APTIMA Trichomonas vaginalis test is cleared for both screening and diagnosis in women 1
• Male testing: NAAT demonstrates superior sensitivity in men but requires laboratory validation for male specimens 1
• Same collection device can be used for concurrent Chlamydia trachomatis/Neisseria gonorrhoeae testing 1

Point-of-Care Testing Options

Wet Mount Microscopy

Wet mount should NOT be relied upon as the sole diagnostic test due to poor sensitivity (40-80%). 1, 2, 3

• Technique: Examine vaginal discharge in saline under microscopy for motile flagellated trichomonads 1
• Critical timing: Must be performed within 30 minutes to 2 hours of collection, as organisms lose motility rapidly 1, 3
• Sensitivity: 40-80% with high false-negative rate 1, 2, 3
• When to use: Immediate point-of-care diagnosis when microscope is available, but always confirm negative results with NAAT 2, 3

Rapid Antigen Testing

• OSOM Trichomonas Rapid Test: Does not require viable organisms 1
• Sensitivity: 62-95% compared to culture and NAAT, with best performance in symptomatic patients 1
• Specimen: Vaginal swab or discharge 1
• Stability: Room temperature for 24 hours 1

Alternative Testing Methods

Culture

• InPouch TV culture system: Allows immediate wet mount review and subsequent culture 1
• Sensitivity: ~70% compared to NAAT 1
• Not widely available and largely superseded by NAAT 1, 2
• When to consider: Recurrent cases when wet mount/KOH is negative 1

DNA Hybridization Probe

• Affirm VP III Assay: Detects T. vaginalis, Gardnerella vaginalis, and Candida albicans 1
• Does not require viable organisms but has lower sensitivity than NAAT 1
• FDA-cleared only for vaginal specimens from symptomatic female patients 1

Recommended Diagnostic Approach

For Symptomatic Women

1. Measure vaginal pH using pH strips (>4.5 suggests trichomoniasis or bacterial vaginosis) 2, 3
2. Perform wet mount immediately if microscope available for rapid diagnosis 2, 3
3. Collect specimen for NAAT regardless of wet mount result 2, 3
4. Test for concurrent STIs: Chlamydia trachomatis, Neisseria gonorrhoeae, and HIV 1

For Asymptomatic High-Risk Women

1. Use NAAT as primary screening test (most sensitive method) 1, 2
2. Collect vaginal swab (self-collection acceptable) or urine specimen 1
3. Screen for concurrent STIs using same specimen when possible 1

For Men (Symptomatic or Partners of Infected Women)

1. NAAT on urine specimen (requires laboratory validation for male specimens) 1
2. Urethral swab if urethritis symptoms present 1
3. Consider empiric treatment of male partners even with negative testing, as organism isolation is difficult in asymptomatic male carriers 4

Critical Pitfalls to Avoid

• Never rely solely on wet mount due to poor sensitivity; negative wet mount does not exclude trichomoniasis 2, 3
• Do not delay wet mount examination beyond 2 hours, as organisms lose motility and become undetectable 1, 3
• Do not use Papanicolaou test for diagnosis due to poor sensitivity and specificity 1
• Do not fail to test sexual partners simultaneously to prevent reinfection 4, 5
• Do not overlook concurrent STIs, as many infections coexist with trichomoniasis 3
• Do not assume negative testing in males excludes infection, as isolation is difficult in asymptomatic male carriers 4

Confirmation of Diagnosis Before Treatment

The FDA drug label for metronidazole requires confirmation of T. vaginalis by appropriate laboratory procedures (wet smears and/or cultures) before treating symptomatic trichomoniasis. 4 However, given the poor sensitivity of wet mount and the high specificity of NAAT, NAAT-positive results are sufficient for diagnosis and treatment initiation. 1, 2