What tests are recommended for STI (Sexually Transmitted Infections) screening?

STI Screening Tests: Recommended Panel and Approach

Screen all sexually active individuals with nucleic acid amplification tests (NAATs) for chlamydia and gonorrhea, serologic testing for syphilis (both treponemal and non-treponemal), HIV testing, and consider trichomoniasis testing for females—with specimen collection sites determined by sexual practices including pharyngeal, rectal, and urethral sites based on exposure history. 1, 2

Core Testing Panel by Pathogen

Chlamydia and Gonorrhea

• Use NAATs exclusively—they offer superior sensitivity (86.1%-100%) and specificity (97.1%-100%) compared to traditional culture methods 1, 3
• For females: vaginal swab NAAT is the preferred specimen 1
• For males: first-catch urine NAAT is the preferred specimen 1
• For men who have sex with men (MSM): collect pharyngeal, rectal, AND urethral specimens based on sexual practices (receptive oral sex, receptive anal intercourse, and insertive intercourse respectively) 4, 2
• Extragenital testing is critical—53% to 100% of pharyngeal and rectal infections are asymptomatic and would be missed with urogenital testing alone 3

Syphilis

• Requires both treponemal AND non-treponemal serologic tests—never rely on a single positive result 1
• Traditional approach: start with non-treponemal test (RPR or VDRL), then confirm positive results with treponemal test (TP-PA, enzyme immunoassay, or chemiluminescent immunoassay) 1
• Reverse sequence screening (treponemal first) is increasingly common but still requires both test types for diagnosis 1

HIV

• Standard HIV testing per local protocols for all at-risk individuals 1
• Screen at initiation of STI evaluation, as any STI increases HIV acquisition and transmission risk 4

Trichomoniasis (Females)

• Vaginal swab NAAT is strongly preferred—wet mount microscopy has poor sensitivity (60-70%) and should be avoided as primary screening 1
• Do not use Papanicolaou tests for diagnosis due to inadequate sensitivity and specificity 1
• Consider screening for women with high-risk behaviors rather than universal screening 2

Population-Specific Screening Frequencies

All Sexually Active Women ≤25 Years

• Annual screening minimum for chlamydia and gonorrhea regardless of reported risk behaviors 4, 2
• This age group has higher infection rates due to cervical immaturity and more frequent partner changes 5

Women >25 Years

• Annual screening if risk factors present: multiple partners, new partner, inconsistent condom use, substance use during sex, or sex work 2

Men Who Have Sex with Men (MSM)

• Annual screening minimum for pharyngeal, rectal, and urethral gonorrhea/chlamydia plus syphilis 4, 2
• Every 3-6 months if higher risk: multiple or anonymous partners, methamphetamine use, sex in conjunction with drug use, or partners with these behaviors 4, 5, 2

Heterosexual Men

• Not universally recommended for asymptomatic men 2
• Consider annual screening in high-prevalence settings (≥2%): jails, juvenile corrections, national job training programs, STD clinics, high school clinics, adolescent clinics 4, 2
• Screen if high-risk behaviors present: multiple partners, inconsistent condom use, substance use during sex 2

Pregnant Women

• Universal screening at first prenatal visit for hepatitis B, HIV, and syphilis 5
• Screen for chlamydia and gonorrhea if <25 years or at increased risk 5
• Repeat syphilis testing in third trimester and at delivery for high-risk women 5
• No infant should be discharged without maternal syphilis status determination 5

HIV-Infected Individuals

• Annual syphilis screening minimum, with testing every 3-6 months for high-risk behaviors 5
• Screen all HIV-infected women for trichomoniasis 2
• Comprehensive STI screening at HIV care initiation 2

High-Risk Populations Requiring Frequent Screening (Every 3-6 Months)

• Commercial sex workers 1
• Individuals with multiple or anonymous sexual partners 4, 2
• Sex in conjunction with illicit drug use 4, 2
• Partners who engage in high-risk behaviors 2
• History of recent STIs 2
• Persons who inject drugs (also screen for hepatitis C, even if only once) 5

Post-Treatment Rescreening Protocol

Rescreen ALL individuals 3 months after treatment for chlamydia or gonorrhea, regardless of whether partners were treated—reinfection rates are high and this is non-negotiable 4, 5, 2

• Consider rescreening females with trichomoniasis at 3 months 4, 2
• If 3-month rescreening is not possible, retest at next healthcare visit within 12 months 2

Critical Pitfalls to Avoid

• Never use wet mount microscopy as primary trichomoniasis screening—60-70% sensitivity misses too many infections 1
• Never diagnose syphilis on a single test—both treponemal and non-treponemal results plus clinical evaluation are required 1
• Never skip extragenital testing in MSM—the majority of pharyngeal and rectal infections are asymptomatic 3
• Never delay treatment if clinical suspicion is high—presumptive treatment may be appropriate to prevent ongoing transmission while awaiting results 1
• Never assume partner treatment occurred—always rescreen at 3 months regardless of reported partner treatment 4, 2

Specimen Collection Based on Sexual Practices

Tailor specimen sites to sexual behavior history, regardless of reported sexual orientation 4:

• Receptive oral sex: pharyngeal swab 2
• Receptive anal intercourse: rectal swab 2
• Insertive vaginal/anal intercourse: urethral specimen (urine for males, vaginal swab for females) 1, 2