Sexually Transmitted Infection (STI) Testing Guidance

Clinical Situation

Recommended Bloodwork

Any STI evaluation (asymptomatic screening OR specific syndromes below)

-HIV (HIV-1/HIV-2 antibody and antigen, LAB473)

-Syphilis screen:

    -If no known prior syphilis: Syphilis, Screen-Treponema pallidum Ab with reflex to RPR (LAB9478)

    -If known prior syphilis: RPR (LAB3351)

Additional testing for select situations:

-Hepatitis B surface antigen (sexual assault, prenatal, more than one sex partner in past 6 months, past or current intravenous substance use, hepatitis B sAg-positive sex partner, men who have sex with men)

-Hepatitis C antibody with reflex to PCR (sexual assault, prenatal, or at least once for all adults)

Clinical Situation

Recommended Site-Specific Testing

Notes

Routine STI screening or victim of sexual assault (asymptomatic)

Chlamydia trachomatis and Neisseria gonorrhoeae qualitative PCR (LAB3477 – send from any relevant sites: oropharyngeal, rectal, vaginal, urine, endocervical)

AVOID ordering STI Panel (LAB3480)

Asymptomatic screening for Mycoplasma genitalium or Trichomonas vaginalis is not recommended for general populations.

The STI panel (LAB3480) or the standalone TV/MG PCR (LAB3471) should not be used for routine screening during pregnancy. Treatment of asymptomatic TV during pregnancy resulted in 1.8 relative risk of preterm birth compared with no treatment in one clinical trial.¹

Some at-risk populations may be considered for asymptomatic Trichomonas vaginalis screening using vaginal specimens (e.g., prior diagnosis of vaginitis due to Trichomonas vaginalis, sex work, transactional sex).

Sex partner of confirmed case (asymptomatic)

Offer empiric treatment for the known pathogen + discuss asymptomatic STI screening if not already complete (see row above and Table 1.)

Cervicitis or pelvic inflammatory disease (PID)

(symptomatic)¹

Preferred initial testing:  Chlamydia trachomatis and Neisseria gonorrhoeae qualitative PCR (LAB3477 from vaginal or cervical swab) AND Bacterial Vaginosis Gram stain (LAB3230)*

OR

If symptoms persist or recur despite prior evaluation and treatment:             STI panel (LAB3480 from vaginal or cervical swab) AND Bacterial                      Vaginosis Gram stain (LAB3230)*  

Observational studies suggest associations between Mycoplasma genitalium and cervicitis (in 10-30% of cases) or PID (in 10% of cases) – however, the benefits of testing or treating for Mycoplasma genitalium in PID remain unproven.^2,3

Trichomonas vaginalis predominantly causes vaginitis and may sometimes cause cervicitis. While Trichomonas vaginalis may sometimes be detected as a co-infection in PID, it is unlikely to be a cause of PID.⁴

Urethritis in individuals with a penis (symptomatic)²

Preferred initial testing:   Chlamydia trachomatis and Neisseria gonorrhoeae qualitative PCR (LAB3477 from urine)

OR

If symptoms persist or recur despite prior evaluation and treatment:   STI panel (LAB3480 from urine)

Recommendations vary on whether Mycoplasma genitalium or Trichomonas vaginalis testing should be included in the initial evaluation of urethritis.

For urethritis in individuals with a penis, Mycoplasma genitalium has been implicated in up to 20-25% of non-Chlamydial/non-gonococcal urethritis cases. Clinicians may choose to include Mycoplasma in initial testing (particularly if there is exposure risk) or reserve Mycoplasma genitalium testing for instances in which N. gonorrhoeae and Chlamydia have been ruled out.

The role of Trichomonas vaginalis in urethritis among individuals with a penis is less clear: infection tends to be asymptomatic in >75% of cases and may sometimes spontaneously clear. Untreated infection can serve as a reservoir for re-infection of sex partners with a vagina.⁵

Evaluation and treatment for Trichomonas as a cause of urethritis is generally limited to cases where contact with an infected partner occurred or symptoms have persisted/recurred despite initial evaluation/treatment.

Urethritis in individuals with a vagina (symptomatic)²

Preferred initial testing:   Chlamydia trachomatis and Neisseria gonorrhoeae qualitative PCR (LAB3477 from urine) + Chlamydia trachomatis and Neisseria gonorrhoeae qualitative PCR (LAB3477 from vaginal swab)

OR

If symptoms persist or recur despite prior evaluation and treatment:  STI panel (LAB3480 from urine)

Trichomonas more commonly causes vaginitis, but can occasionally cause urethritis or cystitis in individuals with a vagina. Evaluation and treatment for Trichomonas as a cause of urethritis is generally limited to cases where contact with an infected partner occurred or symptoms have persisted/recurred despite initial evaluation/treatment.

Mycoplasma genitalium is not clearly implicated as a cause or urethritis in individuals with a vagina/cervix.⁶

Vaginitis

(symptomatic)³

Preferred initial testing:  STI panel (LAB3480 from vaginal swab) + Bacterial Vaginosis Gram stain (LAB3230)*

Recommendations vary on whether traditional microscopy or nucleic acid amplification tests should be the preferred tests for initial evaluation of vaginitis. While NAAT may have higher sensitivity for many infections (NAAT is likely more sensitive for detecting Trichomonas than wet prep/microscopy), NAAT may also risk false positive results with detection of low-levels of normal flora (e.g., Candida).

Mycoplasma genitalium does not have a clear role in causing vaginitis. However, there is no option for testing for TV alone or CT/NG/TV without MG at this time. Providers and patients should be prepared for how to respond to MG positive results.

Note that while the STI panel includes Trichomonas, microscopy is still needed to assess for vaginal Candidiasis or bacterial vaginosis.

Genital or anorectal ulcers (symptomatic)

HSV PCR (LAB945 from swab of unroofed lesion)

Syphilis screen (from blood)

Consider mpox PCR (swab from lesion LAB3281) in select cases based on clinical features/epidemiologic risk (See mpox toolkit.)

Other rarer infectious causes of genital or anorectal ulcers include lymphogranuloma venereum (LGV, due to Chlamydia trachomatis L serovar) or chancroid (due to Haemophilus ducreyi)   require separate referral lab testing or empiric syndromic treatment. Consider ID consult or e-comm.

Proctitis or proctocolitis

Chlamydia trachomatis and Neisseria gonorrhoeae qualitative PCR (LAB3477 from rectal swab)

Separate referral lab testing is required if suspecting proctocolitis due to lymphogranuloma venereum (LGV, due to Chlamydia trachomatis L serovar) as indicated above