What type of test is used for diagnosing trichomoniasis?

Diagnostic Testing for Trichomoniasis

Nucleic acid amplification testing (NAAT) is the preferred diagnostic test for trichomoniasis, offering superior sensitivity (95-100%) compared to all other methods and accepting multiple specimen types including vaginal swabs, endocervical swabs, urine, and liquid-based cytology specimens. 1

Primary Diagnostic Method: NAAT

• NAAT should be used as the first-line diagnostic test when available, as recommended by the CDC, because it provides the highest sensitivity and does not require viable organisms for detection 1
• The FDA-cleared APTIMA Trichomonas vaginalis test demonstrates 100% sensitivity for vaginal swabs, endocervical swabs, and ThinPrep samples, with 95.2% sensitivity for urine specimens 2
• Multiple specimen types are acceptable: vaginal swabs, endocervical swabs, urine, liquid-based cytology specimens, urethral swabs, rectal swabs, and pharyngeal swabs 3
• Specimens remain stable at room temperature for 7 days (or per manufacturer's recommendations), providing flexibility in transport and processing 3
• NAAT performs equally well in both symptomatic and asymptomatic patients, making it ideal for screening high-risk populations 2

Alternative Diagnostic Methods (When NAAT Unavailable)

Rapid Antigen Tests

• The OSOM Trichomonas Rapid Test is the best alternative when NAAT is unavailable, with sensitivity ranging from 62% to 95% compared to culture and NAAT, performing best in symptomatic patients 3, 1
• Results are available in 15 minutes and do not require live organisms for optimal test performance 4

Culture

• The InPouch TV culture system allows both immediate smear review by wet mount and subsequent culture, with approximately 70% sensitivity compared to NAAT 3
• Culture is not widely available and has been largely superseded by NAAT 1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 3
• This test is FDA-cleared only for vaginal specimens from symptomatic female patients 3

Methods to Avoid as Primary Diagnostic Tests

Wet Mount Microscopy

• Wet mount should never be relied upon as the sole diagnostic test due to poor sensitivity of only 40-80%, meaning it will miss 20-60% of true infections 1
• The test requires live organisms to visualize movement and must be performed within 30 minutes to 2 hours of specimen collection 3, 1
• If wet mount is negative but clinical suspicion is high (vaginal pH >4.5, risk factors for STIs), more sensitive tests such as NAAT must be used 1

Clinical Algorithm for Diagnosis

1. For any woman with vaginal discharge and pH >4.5, or patients with STI risk factors: Order NAAT testing on vaginal swab, endocervical swab, or urine 1

2. If NAAT is unavailable: Use rapid antigen testing (OSOM) for symptomatic patients, which provides results in 15 minutes 1

3. If microscopy is immediately available: Perform wet mount to check for motile trichomonads, but always confirm negative results with NAAT or rapid antigen testing 1

4. For screening asymptomatic high-risk populations (multiple sexual partners): Use NAAT, which maintains high sensitivity even in asymptomatic infections 1, 2

Critical Pitfalls to Avoid

• Never exclude trichomoniasis based on a negative wet mount alone, as sensitivity is only 40-80% 1
• Do not delay wet mount examination beyond 2 hours, as organisms lose motility and become undetectable 1
• Remember that up to 50% of trichomoniasis infections are asymptomatic, so absence of symptoms does not exclude infection 1
• Always evaluate and treat sexual partners simultaneously to prevent reinfection 1