Sexually Transmitted Infections

Sexually transmitted infections (STIs) constitute a major health burden in the U.S., and reported incidence among adolescents is increasing. These diseases are frequently asymptomatic and are most often caused by viruses or bacteria.

Diagnosis

Indications for Testing

  • Symptomatic individuals
    • Urgency, frequency, dysuria in the absence of a documented urinary tract infection (UTI)
    • Vaginal or penile discharge
    • Pelvic pain
    • Prostatitis symptoms
    • Genital lesions – painful vesicles, nonpainful shallow ulcer
  • Asymptomatic individuals – see Screening for testing recommendations

Laboratory Testing

  • CDC – testing recommendations
  • Refer to the following ARUP Consult topics for sexually transmitted infection (STI) testing recommendations for
  • STI testing methods
    • Wet mount
      • Bacterial vaginosis – presence of clue cells is diagnostic in appropriate clinical setting
    • Nucleic acid amplification testing (NAAT)
      • Preferred for detecting Chlamydia trachomatis and Neisseria gonorrhoeae in a variety of specimens (U.S. Preventive Services Task Force [USPSTF], 2014; CDC, 2014)
      • Most sensitive test for Trichomonas vaginalis
      • Highly sensitive and specific
      • Specimen collectionfor optimal specimen types and collection instructions, refer to ARUP's Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests
    • Culture
      • C. trachomatis
        • Not recommended for routine detection
        • May be considered for anatomic locations for which amplified testing has not been validated
        • May be used in medicolegal settings and to assess suspected treatment failure
        • High specificity; less sensitive than NAAT
      • N. gonorrhoeae
        • Not recommended for routine detection
        • Recommended in combination with antimicrobial susceptibility testing in cases of suspected or documented treatment failure
        • May be considered for anatomic locations for which amplified testing has not been validated
        • Sensitivity dependent on transport time viability declines rapidly during transport
      • T. vaginalis – not recommended for routine detection
    • DNA probes and direct fluorescent antibody (DFA)
      • Not recommended for routine detection
      • Lower sensitivity than NAAT

Differential Diagnosis

Screening

Specimen Collection

Women

Men

Extragenital Sites

  • Women (CDC, 2014)
    • No recommendations due to scarcity of published studies; however, available data suggests rectal and oropharyngeal infections are not uncommon in women
    • Consider screening women with known risk factors
  • Men (CDC, 2014)
    • Extragenital infections are common and mostly asymptomatic – most frequent for men who have sex with men (MSM) with multiple or anonymous sexual partners
    • Screening recommended at least annually in MSM
      • Rectal specimen for men who have receptive anal intercourse
      • Pharyngeal specimen for men who have receptive oral intercourse

HIV-Positive Individuals

CDC STI Screening Recommendations for HIV-Positive Individuals
STI CDC Recommendation

Chlamydia

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

Gonorrhea

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

Syphilis

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

Trichomonas

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

HBV

Test for HBsAg and anti-HBc and/or anti-HBs27

HCV

All persons at initial evaluation of HIV

Annually for MSM

HSV

Consider type-specific testing

HPV

All women within 1 yr of sexual activity or initial HIV diagnosis with conventional or liquid-based cytology; repeat 6 mos later

CDC, Centers for Disease Control and Prevention; HBV, hepatitis B virus; HCV, hepatitis C virus; HPV, human papillomavirus; HSV, herpes simplex virus; MSM, men who have sex with men; STI, sexually transmitted infection

Women Who Have Sex with Women (WSW)

  • Due to high rates of heterosexual activity in this population, STI screening should reflect individual partner type and reported activity (Wangu, 2017)

Transgender Individuals

  • STI screening should be based on current anatomy and sexual practices (Wangu, 2017)

Background

Most Common Viral STIs

Most Common Bacterial STIs

Chlamydia trachomatis

  • Epidemiology
    • Incidence – 643/100,000 for females; 262/100,000 for males (CDC, 2014); most common reportable STI in U.S. and worldwide
    • Age – highest incidence in 15-24 years
    • Gram-negative obligate intracellular parasite
  • Risk factors
    • >1 sex partner, a new sex partner, or a sex partner with multiple partners
    • Sex partner with an STI
    • Intermittent or lack of condom use
    • Previous or current STI
    • Exchange of sex for money or drugs
  • Clinical presentation
    • Asymptomatic in >50% of infected patients
    • Urethritis, salpingitis, epididymo-orchitis, prostatitis
    • Oropharyngeal disease
    • Pelvic inflammatory disease (PID)
    • Infection during pregnancy increases risk of
      • Premature rupture of membranes
      • Preterm delivery
      • Low birth weight
      • Neonatal conjunctivitis
      • Neonatal pneumonia
    • Complications
      • Ectopic pregnancy
      • Tubal factor infertility

Bacterial vaginosis (BV)

  • Epidemiology
    • Prevalence – 10-30% of pregnant women (American Pregnancy Association, 2015); most common form of vaginitis (≥50% of women with BV are asymptomatic)
    • Polymicrobial – caused by a combination of Gardnerella vaginalis with anaerobic bacteria overgrowth at the expense of commensal lactobacilli
  • Risk factors
    • Douching
    • Nonuse of barrier methods
    • Multiple sex partners (>2)
  • Clinical presentation
    • Malodorous vaginal discharge (fishy odor)
    • Vulvovaginitis, cervicitis, salpingitis
    • Infection during pregnancy increases risk of
      • Acquisition and transmission of HIV
      • Preterm labor
      • Premature rupture of membranes
      • Postpartum endometriosis

Neisseria gonorrhoeae (gonorrhea)

  • Epidemiology
    • Incidence – 108/100,000 for females; 106/100,000 for males (CDC, 2014)
    • Age – highest incidence in 15-24 years
    • Nonmotile gram-negative diplococcus
  • Risk factors
    • >1 sex partner, a new sex partner, or a sex partner with multiple partners
    • Sex partner with an STI
    • Intermittent or lack of condom use
    • Previous or current STI
    • Exchange of sex for money or drugs
  • Clinical presentation
    • Cervicitis, urethritis, salpingitis
    • Pelvic inflammatory disease (PID)
    • Oropharyngeal disease
    • Neonatal infection
    • Proctitis (predominantly in men who have sex with men)

Treponema pallidum (syphilis)

Most Common Parasitic/Protozoan STI

Trichomonas vaginalis

  • Epidemiology
    • Prevalence – ~3 million in U.S. (CDC, 2015)
    • Age – highest incidence in 30-50 years
    • Flagellated protozoan
  • Risk factors
    • >1 sex partner, a new sex partner, or a sex partner with multiple partners
    • Sex partner with an STI
    • Intermittent or lack of condom use
    • Previous or current STI
    • Exchange of sex for money or drugs
    • Coinfection with gonorrhea or HIV
  • Clinical presentation
    • In females, symptoms include malodorous vaginal discharge, strawberry cervix, dysuria, vulvar irritation, vaginitis, and cervicitis
      • >50% of women with T. vaginalis infections have minimal or no symptoms
      • Trichomaniasis accounts for 15-20% of cases of vulvovaginitis
    • In males, T. vaginalis causes urethritis, epididymitis, prostatitis
    • Infection during pregnancy increases risk of
      • HIV transmission
      • Preterm labor
      • Premature rupture of membranes
      • Low birth weight

ARUP Lab Tests

Primary Tests

Detect Chlamydia trachomatis and Neisseria gonorrhoeae in a variety of specimens

Positive results are confirmed using an alternate nucleic acid target

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Culture may be required in certain clinical contexts for diagnosing C. trachomatis and N. gonorrhoeae infections

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

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Preferred test for detecting C. trachomatis and N. gonorrhoeae in variety of specimens

Requires APTIMA collection kit

Does not include confirmation of positive results by an alternate nucleic acid target; if confirmation of positive results by an alternate nucleic acid target is required, please refer to C. trachomatis and N. gonorrhoeae by transcription-mediated amplification (TMA) with confirmation

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Culture may be required in certain clinical contexts for diagnosing C. trachomatis and N. gonorrhoeae infections

Detect C. trachomatis and N. gonorrhoeae in ThinPrep specimens

Does not include confirmation of positive results by an alternate nucleic acid target; if confirmation of positive results by an alternate nucleic acid target is required, please refer to C. trachomatis and N. gonorrhoeae by TMA with confirmation

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Culture may be required in certain clinical contexts for diagnosing C. trachomatis and N. gonorrhoeae infections

Aid in the diagnosis of bacterial vaginosis, vulvovaginal candidiasis, and trichomoniasis

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Aids in the diagnosis of bacterial vaginosis by detection of Lactobacillus (L. gasseri, L. crispatus, and L. jensenii), Gardnerella vaginalis, and Atopobium vaginae

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Detect T. vaginalis in various specimens

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Performance of test on self-collected vaginal swab specimens and those from pregnant women has not been evaluated

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

Does not include confirmation of positive results by an alternate nucleic acid target; if confirmation of positive results by an alternate nucleic acid target is required, please refer to C. trachomatis and N. gonorrhoeae by TMA with confirmation

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Culture may be required in certain clinical contexts for diagnosing C. trachomatis and N. gonorrhoeae infections

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

Does not include confirmation of positive results by an alternate nucleic acid target; if confirmation of positive results by an alternate nucleic acid target is required, please refer to C. trachomatis and N. gonorrhoeae by TMA with confirmation

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Culture may be required in certain clinical contexts for diagnosing C. trachomatis and N. gonorrhoeae infections

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

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

Nucleic amplification testing is recommended for detection of C. trachomatis from endocervical or urethral specimens; refer to C. trachomatis by TMA

Can detect N. gonorrhoeae in specimens not approved for nucleic acid amplification testing

Preferred testing is combined C. trachomatis and N. gonorrhoeae by TMA​

Related Tests

SurePath media is not preferred when testing for Chlamydia trachomatis and Neisseria gonorrhoeae by transcription-mediated amplification (TMA)

Preferred test is C. trachomatis and N. gonorrhoeae by TMA, or, if confirmation of positive results by an alternate nucleic acid target is required, refer to C. trachomatis and N. gonorrhoeae by TMA with confirmation

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

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

Culture may be required in certain clinical contexts for diagnosing C. trachomatis and N. gonorrhoeae infections

Viral transport media (eg, M4/UTM) are not preferred for C. trachomatis and N. gonorrhoeae by TMA

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

The preferred test is C. trachomatis and N. gonorrhoeae by TMA, or, if confirmation of positive results by an alternate nucleic acid target is required, refer to C. trachomatis and N. gonorrhoeae by TMA with confirmation

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Detect and speciate Ureaplasma parvum, Ureaplasma urealyticum, Mycoplasma hominis, and Mycoplasma genitalium; consider ordering for cases of nongonococcal urethritis

Aids in the diagnosis of vulvovaginal candidiasis and trichomoniasis by detection of Trichomonas vaginalis, Candida glabrata, and other Candida species (C. albicans, C. parapsilosis, C. dubliniensis, and C. tropicalis)

Refer to Sample Collection for the Diagnosis of STD Using Nucleic Acid Amplification Tests for optimal specimen types and collection instructions

Detect common vaginal pathogens associated with vaginitis/vaginosis

Not recommended as stand-alone test for sexually transmitted infection testing or screening

Panel includes Candida spp, Gardnerella vaginalis, and Trichomonas vaginalis

Use to detect Mycoplasma hominis and Ureaplasma spp

Not recommended for routine detection of gonorrheal disease

Limited value in the diagnosis of most oculogenital (eg, eyes, genitalia) chlamydial infections

Limited value in the diagnosis of most oculogenital (eg, eyes, genitalia) chlamydial infections

Limited value in the diagnosis of most oculogenital (eg, eyes, genitalia) chlamydial infections

Medical Experts

Contributor

Fisher

Mark A. Fisher, PhD, D(ABMM)
Associate Professor of Clinical Pathology, University of Utah
Medical Director, Bacteriology, Special Microbiology, and Antimicrobial Susceptibility Testing, ARUP Laboratories
Contributor

References

Additional Resources
  • 27272584

    Cantor AG, Pappas M, Daeges M, et al. Screening for Syphilis: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA. 2016; 315 (21): 2328-37.
    PubMed
  • Resources from the ARUP Institute for Clinical and Experimental Pathology®