Sexually Transmitted Infections

Diagnosis

Indications for Testing

• Cervicitis, urethritis, pelvic inflammatory disease, amongst others

Laboratory Testing

• CDC - testing recommendations
• STI testing methods
  • Nucleic acid amplification testing (NAAT)
    • Preferred for detecting C. trachomatis and N. gonorrhoeae in a variety of specimens
    • Highly sensitive and specific
  • 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 preferred testing – NAAT preferred for sensitivity and specificity
      • Recommended in combination with antimicrobial susceptibility testing in cases of suspected or documented treatment failure
      • May be considered if NAAT has not been validated for particular specimen type
      • Sensitivity dependent on transport time
        • N. gonorrhoeae is fastidious; viability declines rapidly during transport
  • DNA probes
    • NAAT testing preferred
  • DFA
    • Not recommended for detecting C. trachomatis
    • Relatively low sensitivity compared to NAAT
• Refer to the following ARUP Consult topics for further STI testing recommendations
  • Human papillomavirus
  • Treponema pallidum
  • HIV
  • Hepatitis B
  • Hepatitis C
  • Herpes simplex virus

Differential Diagnosis

• Urinary tract infection
• Vaginitis/cervicitis
• Vulva, vaginal candidiasis
• Malignancy – ovarian cancer, cervical cancer
• Nephrolithiasis
• Ectopic pregnancy
• Diverticulitis
• Inflammatory bowel disease
• Appendicitis
• Pregnancy
• Ovarian cyst

Screening

Clinical Background

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.

• Most-common viral STIs
  • Human immunodeficiency virus (HIV)
  • Herpes simplex virus
  • Human papillomavirus
• Most-common bacterial STIs
  • Chlamydia trachomatis

    Epidemiology Incidence – 496.5/100,000 females (2008); most common reportable STI in U.S. and worldwide Age – highest incidence is 15-25 years Gram-negative obligate intracellular parasite Risk Factors Multiple sex partners (≥2) Non-Caucasian Younger age (<25 years) Coinfection with gonorrhea or HIV Non-use of barrier methods Previous history of STI Clinical Presentation Asymptomatic in >50% of infected patients Urethritis, salpingitis, epididymo-orchitis Oropharyngeal disease Pelvic inflammatory disease (PID) Infection during pregnancy Premature rupture of membranes Preterm delivery Low birth weight Neonatal conjunctivitis Neonatal pneumonia Complications Ectopic pregnancy Tubal factor infertility

    Bacterial vaginosis (BV)

    Epidemiology Prevalence – 16% of pregnant women; most common form of vaginitis (50% of women with BV are asymptomatic) Caused by a combination of Gardnerella vaginalis with anaerobic bacteria overgrowth at the expense of commensal lactobacilli Polymicrobial Risk Factors Douching Non-use of barrier methods Multiple sex partners (>2) Non-Caucasian Clinical Presentation Malodorous vaginal discharge (fishy odor) Vulvovaginitis, cervicitis, salpingitis Infection during pregnancy Increased risk of HIV infection Preterm labor Premature rupture of membranes Postpartum endometriosis

    Neisseria gonorrhoeae

    Epidemiology Incidence – 118.9/100,000 in 2007 (U.S.) Age – highest incidence is 15-25 years Nonmotile gram-negative diplococcus Risk Factors Multiple sex partners (>2) Non-Caucasian Younger age (<25) Coinfection with HIV Non-use of barrier methods Previous history of STI Douching Clinical Presentation Cervicitis, urethritis, salpingitis PID Oropharyngeal disease Neonatal infection

  • Treponema pallidum (syphilis)
• Most-common parasitic/protozoan STI
  • Trichomonas vaginalis

    Epidemiology Prevalence – 7 million cases annually in U.S. Age – highest incidence is 30-50 years  Flagellated protozoan Risk Factors Multiple sex partners (>2) Non-Caucasian Coinfection with gonorrhea or HIV Non-use of barrier methods Previous history of STI Infected with HIV Clinical Presentation Up to 50% of women with T. vaginalis infections have minimal or no symptoms If symptomatic, T. vaginalis infections can cause vaginitis, urethritis, and cervicitis May present with vaginal, malodorous discharge, strawberry cervix, dysuria, and vulvar irritation (accounts for 15-20% of cases of vulvovaginitis) Pregnant females Increased risk of HIV transmission Preterm labor Premature rupture of membranes Low birth weight

Treatment

• CDC recommends treatment of all STIs (see treatment guidelines)

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Ureaplasma Species and Mycoplasma hominis Culture 0065031 Method: Culture	Use to detect Mycoplasma hominis and Ureaplasma spp Use if clinical suspicion exists and all other testing is negative Other than lung transplant specimens, this test is not appropriate for adult respiratory specimens
Vaginal Pathogens DNA Direct Probes 0065153 Method: Qualitative Nucleic Acid Probe	Use to detect common vaginal pathogens associated with vaginitis/vaginosis For T. vaginalis, preferred test is one of the nucleic acid amplification tests (NAAT) Not recommended as stand-alone test for sexually transmitted infection testing or screening
Neisseria gonorrhoea Antibodies, Total 0099685 Method: Semi-Quantitative Complement Fixation	Not recommended  Less sensitive than amplification-based methods