Which sexually transmitted infections should be screened for in a sexually active individual with new, multiple, or anonymous partners?

STI Screening for Sexually Active Individuals with New, Multiple, or Anonymous Partners

All sexually active individuals with new, multiple, or anonymous partners should receive comprehensive screening for chlamydia, gonorrhea, syphilis, and HIV at least annually, with screening frequency increased to every 3–6 months for those with ongoing high-risk behaviors.

Core Screening Panel

The following tests must be performed for all patients in this risk category:

• Chlamydia and gonorrhea: Use nucleic acid amplification tests (NAATs) on first-catch urine specimens for men, or vaginal swabs (preferred) for women 1
• Syphilis: Both a nontreponemal test (RPR or VDRL) AND a treponemal test (EIA or CIA) must be performed together—a single test is insufficient 1, 2
• HIV: Laboratory-based antigen/antibody combination testing 1, 2
• Hepatitis B: Serologic testing (HBsAg and antibodies) if not previously vaccinated 1, 2
• Trichomoniasis (women): Vaginal swab NAAT 1
• Hepatitis C: Consider screening when additional risk factors are present, such as substance use or multiple partners 2

Site-Specific Testing Based on Sexual Practices

Testing must be tailored to anatomic sites of exposure, as infections are often site-specific and asymptomatic:

• Receptive anal intercourse: Rectal swab NAAT for both chlamydia and gonorrhea (laboratory must have validated the assay for rectal specimens) 1, 2
• Receptive oral sex: Pharyngeal swab NAAT or culture for gonorrhea only—pharyngeal chlamydia testing is not recommended due to limited clinical utility 1, 2
• Vaginal/urethral intercourse: Urine NAAT for men; vaginal swab NAAT (preferred) or cervical swab for women 1

Critical pitfall: Relying solely on urine specimens in men who have sex with men misses the majority of rectal and pharyngeal infections, which are often asymptomatic 2. Research demonstrates that 98% of pharyngeal and anorectal infections are missed when only genitourinary screening is performed 3.

Screening Frequency Algorithm

The screening interval depends on the presence of ongoing risk factors:

Standard-Risk Individuals (Annual Screening)

• Stable relationship with mutual monogamy
• No additional risk factors present 1, 2

High-Risk Individuals (Every 3–6 Months)

Screening must be intensified to every 3–6 months when ANY of the following are present:

• Multiple or anonymous partners 1, 2
• New partners since last visit 1, 2
• Substance use during sex, especially methamphetamine 1, 2
• Prior STI diagnosis within the past year 1, 2
• Unprotected sex outside a mutually monogamous relationship 1, 2
• Exchange of sex for drugs or money, or partners who engage in these behaviors 1
• Partner with known STI or high-risk behaviors 1, 2
• Recent life changes (e.g., relationship dissolution) that promote high-risk sexual activity 1

Evidence strength: The recommendation for 3–6 month screening intervals in high-risk populations is supported by modeling studies showing that biannual screening of sexually active MSM could avert 72% of gonorrhea and 78% of chlamydia infections over 10 years 4.

Special Considerations for Men Who Have Sex With Men (MSM)

MSM require comprehensive anatomic-site testing at minimum annually, with the following components:

• Urine/urethral NAAT for chlamydia and gonorrhea 1, 2
• Rectal NAAT for chlamydia and gonorrhea when receptive anal intercourse occurs 1, 2
• Pharyngeal NAAT or culture for gonorrhea when receptive oral intercourse occurs 1, 2
• Syphilis serology (both nontreponemal and treponemal tests) 1, 2
• HIV testing 1, 2
• Consider HSV-2 type-specific serology if contemplating suppressive antiviral therapy 1

MSM with higher-risk profiles (frequent partner change, anonymous partners, substance use during sex) should be screened every 3–6 months 1, 2. Research shows that HIV-negative MSM on PrEP have the highest proportion of infections (47%), followed by HIV-negative MSM not on PrEP (22%) and HIV-positive MSM (20%) 3.

Retesting After Positive Results

Mandatory retesting at 3 months after any positive chlamydia or gonorrhea result, regardless of partner treatment, because reinfection rates range from 25% to 40% 1, 2. This applies even when partners are treated, as reinfection occurs rapidly—within 3.6 months for chlamydia and 6 months for gonorrhea in 25% of previously infected individuals 5.

Common Pitfalls to Avoid

• Testing only one anatomic site: Failing to screen all sites of exposure leads to missed infections, as many STIs are asymptomatic and site-specific 2, 6. Extra-genital infections are prevalent, with 98% of pharyngeal/anorectal infections missed when only genitourinary screening is performed 3
• Single annual screening for ongoing high-risk behaviors: A single annual screen is inadequate for individuals with continuous high-risk behaviors; a 3–6 month interval is required 1, 2
• Omitting treponemal testing for syphilis: Both nontreponemal and treponemal tests must be performed together to avoid false-negative or false-positive results 1, 2
• Accepting patient self-report of consistent condom use as reassurance: Condom effectiveness studies show inconsistent findings due to variations in actual versus reported use, and condoms provide incomplete protection against all STIs 5

Additional Considerations

For individuals with very recent high-risk exposure (within 72 hours): Consider post-exposure prophylaxis with doxycycline 200 mg for bacterial STI prevention in MSM, though this window may have passed for many patients presenting for screening 5, 7. Initial testing can still be performed, but repeat testing at 1–2 weeks may be necessary if initial tests are negative and no presumptive treatment was given 5.

Provider communication is critical: Research shows that MSM who have providers who initiate conversations about sex are significantly more likely to receive appropriate rectal STI screening 8. Obtaining a focused sexual history covering number of partners, types of sexual contact, condom use, partner risk factors, and substance use during sex is essential 5.