What are the clinical diagnostic approaches for trichomoniasis, chlamydia, and gonococcal (Neisseria gonorrhoeae) infection in a patient with a history of sexually transmitted infections (STIs)?

Clinical Diagnosis of Trichomoniasis vs Chlamydia vs Gonococcal Infection

You cannot reliably distinguish between trichomoniasis, chlamydia, and gonorrhea based on clinical features alone—nucleic acid amplification tests (NAATs) are required for accurate diagnosis, as 50-100% of these infections are asymptomatic or have overlapping presentations. 1, 2

Key Diagnostic Principle

All three infections require laboratory confirmation because clinical diagnosis is unreliable. 1, 3 The classic teaching that trichomoniasis causes frothy yellow-green discharge, chlamydia causes mucopurulent cervicitis, and gonorrhea causes purulent discharge cannot be uniformly relied upon for diagnosis. 4

Diagnostic Algorithm

Step 1: Obtain NAATs for All Three Pathogens Simultaneously

• NAATs are the preferred diagnostic method with sensitivity >95% and specificity >99% for gonorrhea and chlamydia, and sensitivity 86-100% for trichomoniasis. 3, 5, 2
• Collect specimens from all sites of penetration: cervical/vaginal swabs in women, urethral swabs or urine in men, plus pharyngeal and rectal swabs if indicated by sexual history. 1, 5
• Self-collected vaginal swabs are FDA-cleared and acceptable for NAAT testing. 3
• Test all patients for all three pathogens plus HIV and syphilis due to high coinfection rates. 3, 6

Step 2: Perform Point-of-Care Microscopy (Limited Utility)

Wet mount microscopy can provide immediate results but has poor sensitivity:

• Detects motile trichomonads in only 50% of infected women. 1, 7, 8
• Shows >10 WBCs per high-power field, which suggests infection but is nonspecific. 1, 4
• Cannot be used to rule out infection if negative. 1

Gram stain (men with urethral discharge only):

• Presence of polymorphonuclear leukocytes with intracellular Gram-negative diplococci is diagnostic for gonorrhea with >99% specificity and >95% sensitivity. 5
• Do not use Gram stain for women, asymptomatic men, or extragenital sites—it is insufficiently sensitive. 5
• Gram stain showing >5 WBCs per oil immersion field without intracellular diplococci indicates nongonococcal urethritis (likely chlamydia). 1

Step 3: Clinical Features That Increase Suspicion (But Do Not Confirm Diagnosis)

Trichomoniasis clues (present in only 50% of cases): 4

• Vaginal discharge with malodor, pruritus, or dysuria. 1
• Strawberry cervix (colpitis macularis) on examination—highly specific but rare. 9
• Elevated vaginal pH >4.5 and positive whiff test. 1
• Multiple sex partners increase risk. 4

Chlamydia/gonorrhea clues (often asymptomatic): 1, 2

• Mucopurulent or purulent cervical discharge. 1
• Cervical friability or bleeding with gentle manipulation. 1
• In men: urethral discharge (purulent suggests gonorrhea, mucopurulent suggests chlamydia, but overlap is common). 1
• Age <25 years, new or multiple partners, inconsistent condom use. 3

Critical caveat: 70% of trichomoniasis and HSV infections, and 53-100% of extragenital gonorrhea/chlamydia infections are asymptomatic. 2

When to Treat Presumptively (Before Test Results)

Treat empirically for gonorrhea and chlamydia in these situations: 1

• High-risk patients unlikely to return for follow-up (adolescents, multiple partners, prior STIs). 1
• High-prevalence settings (STD clinics, certain geographic areas). 3
• Sexual assault survivors. 1

Recommended presumptive regimen: 1

• Ceftriaxone 500 mg IM for gonorrhea PLUS
• Azithromycin 1 g PO or doxycycline 100 mg PO twice daily for 7 days for chlamydia 1, 10
• Add metronidazole 2 g PO single dose or tinidazole 2 g PO single dose for trichomoniasis if suspected. 11, 12, 9

Common Diagnostic Pitfalls to Avoid

• Never rely on negative wet mount to exclude trichomoniasis—sensitivity is only 50%. 1, 7
• Never use Gram stain alone for women or asymptomatic men—it misses most infections. 5
• Never test for only one pathogen—coinfection rates are high and all three require different treatments. 3, 6
• Never use urine-based testing exclusively for trichomoniasis in women—vaginal specimens are required for adequate sensitivity. 8
• Never use non-FDA-cleared NAATs for extragenital sites without laboratory validation. 5

Follow-Up Testing Requirements

• Retest all patients at 3 months after treatment for gonorrhea or chlamydia due to high reinfection rates (not test-of-cure). 6
• Test-of-cure is NOT routinely recommended unless symptoms persist, pregnancy is involved, or pharyngeal gonorrhea was treated. 1
• Repeat testing at 2 weeks if initial tests were negative and no presumptive treatment was given. 6

Partner Management

All sex partners from the past 60 days must be notified, examined, and treated if any infection is diagnosed. 3, 6 Both patients and partners must abstain from intercourse for 7 days after single-dose therapy or until completion of 7-day regimens. 1, 6