Sexually Transmitted Infections

Sexually transmitted infections (STIs) constitute a major health burden in the United States, and the reported incidence is increasing annually. These diseases are frequently asymptomatic and are most often caused by viruses or bacteria.  Some of the most common viral STIs are caused by HIV and human papillomavirus (HPV). The most common bacterial STIs are chlamydia, gonorrhea, and syphilis. Protozoans may also cause STIs; the most common example of this is Trichomonas vaginalis. STIs can have severe health consequences and, if left untreated, can lead to complications that include pelvic inflammatory disease, infertility, cervical cancer, and chronic pelvic pain. Additionally, STIs such as syphilis and trichomoniasis are associated with an increased risk of HIV acquisition and transmission. Laboratory testing is important for the screening and diagnosis of STIs. Appropriate screening prevents the spread of disease, and accurate diagnosis enables appropriate treatment and patient management. 

Quick Answers for Clinicians

What factors should be considered when collecting specimens for suspected sexually transmitted infections?

Specimen type and collection vary based on disease and are important for accurate laboratory testing results. For optimal specimen types and collection instructions for sexually transmitted infection (STI) laboratory testing, refer to ARUP's STI Testing Using Nucleic Acid Amplification Tests–Sample Collection Instructions.

Where can I find additional information about sexually transmitted infection screening, diagnosis, and treatment?

The CDC provides detailed information about sexually transmitted infections (STIs), including screening recommendations, treatment guidelines, data and statistics, and other disease-specific information. 

Which other infections may be important to consider for evaluation during an STI screening or workup?

Bacterial vaginosis, herpes simplex virus (HSV), hepatitis B virus (HBV), hepatitis C virus (HCV), and human papillomavirus (HPV) may also be sexually transmitted and are often included in an STI screening or workup. More information about these conditions may be found in the associated ARUP Consult topics or on the CDC website. 

Indications for Testing

Laboratory testing to screen asymptomatic individuals is appropriate for most individuals. The Screening section provides detailed screening recommendations based on population.

Laboratory testing for the diagnosis of an STI is appropriate for individuals experiencing:

  • Urgency, frequency, or dysuria in the absence of a documented urinary tract infection (UTI)
  • Vaginal or penile discharge
  • Pelvic pain
  • Prostatitis symptoms
  • Genital lesions such as painful vesicles or nonpainful shallow ulcers

Laboratory Testing

Screening

Screening for STIs is important to control the spread of these diseases because many STIs may be asymptomatic. The recommendations for screening vary by disease and population. The tables that follow detail the screening recommendations for chlamydia, gonorrhea, and trichomoniasis in women, pregnant women, men, men who have sex with men (MSM), and persons with HIV. For transgender individuals, STI screening should be based on current anatomy and sexual practices.  For detailed information about screening for syphilis, HIV, and herpes simplex virus (HSV), visit the corresponding ARUP Consult topics.

Refer to ARUP's STI Testing Using Nucleic Acid Amplification Tests–Sample Collection Instructions to determine the optimal specimen types and for collection instructions.

Screening Recommendations for Chlamydia
Population Testing Recommended in These Patients/Circumstancesa

Women

Sexually active women <25 yrs and sexually active women ≥25 yrs who are at increased riskb

Pregnant women

All pregnant women <25 yrs and those ≥25 yrs who are at increased riskb; retest women <25 yrs or those at risk in third trimesterb

Men

No screening recommended,c but consider screening young men in high-prevalence clinical settings or in populations with high burden of infection

MSM

All MSM annually at sites of contact

Repeat testing every 3-6 mos in those at increased riskd

Persons with HIV

All sexually active individuals at first HIV evaluation, then at least annually

More frequent screening may be appropriate depending on risk behaviors and local epidemiology

aUnless otherwise noted, all recommendations come from the CDC. 

bThe CDC defines persons at increased risk as those who have a new sexual partner, >1 sexual partner, a sexual partner with concurrent partners, or a sexual partner who has an STI. 

cThe USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening men for chlamydia and gonorrhea. 

dAll MSM, including those with HIV infection, if risk behaviors persist or if they or their sexual partners have multiple partners. 

Sources: CDC ; USPSTF, 2014 

Screening Recommendations for Gonorrhea
Population Testing Recommended in These Patients/Circumstancesa

Women

Sexually active women <25 yrs and sexually active women ≥25 yrs who are at increased riskb,c

Pregnant women

All pregnant women <25 yrs and those ≥25 yrs who are at increased riskb

Men

No screening recommendedd

MSM

Annually at sites of contact

Repeat testing every 3-6 mos in those at increased risk

Persons with HIV

All sexually active individuals at first HIV evaluation, then at least annually

More frequent screening may be appropriate depending on risk behaviors and local epidemiology

aUnless otherwise noted, all recommendations come from the CDC. 

bThe CDC defines persons at increased risk as those who have a new sexual partner, >1 sexual partner, a sexual partner with concurrent partners, or a sexual partner who has an STI. 

cAdditional risk factors for gonorrhea include inconsistent condom use among persons who are not in mutually monogamous relationships, previous or coexisting STIs, and exchanging sex for money or drugs; clinicians should consider the communities they serve and may opt to consult local public health authorities for guidance to identify groups that are at increased risk. 

dThe USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening men for chlamydia and gonorrhea. 

eAll MSM, including those with HIV infection, if risk behaviors persist or if they or their sexual partners have multiple partners. 

Sources: CDC ; USPSTF, 2014 

Screening Recommendations for Trichomoniasis
Population Testing Recommended in These Patients/Circumstancesa

Women

There are no recommendations for routine asymptomatic screening for T. vaginalis

Screening may be considered in women in areas of high prevalence (eg, STI clinics and correctional facilities) and in women at high riskb

Persons with HIV

Sexually active women at entry to care, then at least annually

aUnless otherwise noted, all recommendations come from the CDC.

bFor example, those with multiple sex partners or history of exchanging sex for payment, illicit drug use, or history of an STI.

Source: CDC 

Diagnosis

Specific testing recommendations for syphilis, HIV, and HSV can be found in the corresponding ARUP Consult topics. Accurate diagnosis is important to determine appropriate treatment and medical management. Nucleic acid amplification testing (NAAT) is recommended for diagnosis of most STIs, although in some cases, culture and serology may be useful.

Refer to ARUP's STI Testing Using Nucleic Acid Amplification Tests–Sample Collection Instructions to determine the optimal specimen types and collection instructions for these laboratory tests.

ARUP Laboratory Tests

Recommended Tests

Preferred test for detecting Chlamydia trachomatis and Neisseria gonorrhoeae in a variety of specimens

Requires APTIMA collection kit

Does not include confirmation of positive results by an alternate nucleic acid target

Use to detect C. trachomatis and N. gonorrhoeae in a variety of specimens

Positive results are confirmed using an alternate nucleic acid target

Preferred test for detecting C. trachomatis, N. gonorrhoeae, and Trichomonas vaginalis in a variety of specimens

Use to detect C. trachomatis and N. gonorrhoeae in ThinPrep specimens

Does not include confirmation of positive results by an alternate nucleic acid target

Use to detect T. vaginalis in various specimens

Refer to the Specimen Collection and Handling document in the Laboratory Test Directory

Use to detect common vaginal pathogens associated with vaginitis/vaginosis

Not recommended as a standalone test for STI testing or screening

Panel includes testing for Candida species, Gardnerella vaginalis, and T. vaginalis

Panel includes Candida spp, Gardnerella vaginalis, and Trichomonas vaginalis

Other Testing (Useful in Certain Clinical Situations)

Preferred test for detecting C. trachomatis in a variety of specimens

Does not include confirmation of positive results by an alternate nucleic acid target

Preferred test for detecting N. gonorrhoeae in a variety of specimens

Does not include confirmation of positive results by an alternate nucleic acid target

Detects but does not differentiate C. trachomatis L1-L3 serovars

SurePath media is not preferred when testing for C. trachomatis and N. gonorrhoeae by transcription-mediated amplification (TMA)

Use of transport media other than APTIMA specimen collection kit may result in reduced sensitivity

The preferred test is Chlamydia trachomatis and Neisseria gonorrhoeae by Transcription-Mediated Amplification (TMA) (0060241)

Not recommended for routine detection of C. trachomatis

Use to detect C. trachomatis in medicolegal settings and to assess suspected treatment failure

May be considered for anatomic locations for which amplified testing has not been validated

Can detect N. gonorrhoeae in specimens not approved for NAAT

Preferred testing is combined Chlamydia trachomatis and Neisseria  gonorrhoeae by Transcription-Mediated Amplification (TMA) (00​60241)

Medical Experts

Medical Reviewer

References

Additional Resources