Updated Screen for Sexually Transmitted Infections

February 2024
Ampath | ampath.co.za

Overview

Sexually transmitted infections (STIs) are highly prevalent, with the World Health Organization (WHO) estimating that over 1 million STIs are acquired globally each day.

The most common causes of genital ulceration, urethral discharge, and vaginal discharge include:

✅ Genital Ulceration

• Most common causes:
  • Herpes simplex virus (HSV) types 1 and 2
  • Treponema pallidum (syphilis)
• Less common causes:
  • Chlamydia trachomatis (serovars L1–L3 – LGV)
  • Haemophilus ducreyi
  • Klebsiella granulomatosis

✅ Male Urethral Discharge

• Most common causes:
  • Neisseria gonorrhoeae
  • Chlamydia trachomatis
• Other possible causes:
  • Mycoplasma genitalium
  • Trichomonas vaginalis

✅ Vaginal Discharge

• Common infectious causes:
  • Neisseria gonorrhoeae
  • Chlamydia trachomatis
  • Trichomonas vaginalis
  • Mycoplasma genitalium
• Non-STI causes:
  • Bacterial vaginosis (BV)
  • Candidiasis

BV and VVC result from disruption of the normal vaginal microbiome, even in patients who are not sexually active.

Why Testing Matters

Although STIs may cause symptoms such as discharge or ulcers, many are asymptomatic, especially:

• Neisseria gonorrhoeae:
  • 45–85% of men symptomatic
  • 14–35% of women symptomatic
• Chlamydia trachomatis:
  • 11–33% of men symptomatic
  • 6–17% of women symptomatic

Complications of Untreated STIs:

• Increased risk of HIV acquisition and transmission
• Pelvic inflammatory disease (PID)
• Tubal infertility
• Ectopic pregnancy
• Stillbirth and congenital infections

Challenges with Syndromic Management

While syndromic treatment is still standard in resource-limited settings, it has limitations:

• Promotes antibiotic resistance due to broad-spectrum use
• Misses asymptomatic infections
• Relies on patient symptom reporting and health-seeking behaviour
• Fails to provide epidemiological data

Updated Testing Recommendations

Where possible, test symptomatic patients, treat based on specific results, and screen asymptomatic patients at risk.

✅ High-Risk Groups: Recommended Screening Intervals

• People living with HIV: At entry to care, then annually
• PrEP users: At entry, then annually based on risk
• Men who have sex with men (MSM): Annually, or every 6 months if high risk
• Transgender and gender-diverse individuals: Annually, or more often if high risk
• Sex workers: Every 3 to 6 months
• Pregnant individuals: At first antenatal visit, and again in the third trimester

Ampath’s Updated STI Screen

Available with or without HIV testing:

• With HIV testing: Mnemonic STD
• Without HIV testing: Mnemonic STDNH
• Turnaround time: 24–48 hours from sample receipt

✅ Tests Included

Serology (blood sample):

• Hepatitis B surface antigen
• Hepatitis C antibody
• Syphilis: RPR and Treponema pallidum antibody
• HIV-1/2 antibody and p24 antigen (only with STD mnemonic)

Molecular (PCR) Testing:

• Neisseria gonorrhoeae
• Chlamydia trachomatis
• Trichomonas vaginalis
• Mycoplasma genitalium

✅ Specimen Types

• Males: First-void urine
• Females:
  • Preferred: Dry vaginal swab (self-collection permitted)
  • Alternative (if swab not feasible): Urine (note: lower sensitivity for N. gonorrhoeae and C. trachomatis)

Site-specific testing (e.g., rectal or throat swabs) may be necessary based on sexual practices.

Additional Notes

• HSV-1 and HSV-2 are not included in the screen.
  • For ulcers, request genital ulcer PCR (dry swab from lesion)
  • HSV-2 IgG may be used for past exposure, but is not recommended in acute cases due to low sensitivity
• For bacterial vaginosis and candidiasis, test using:
  • Vaginal swab with Nugent scoring, microscopy, and culture
  • Optional bacterial vaginosis PCR

Further Reading

• Lab Update 9 – Bacterial Vaginosis PCR
• Lab Update 44 – Genital Ulcer Multiplex PCR
• Ampath Chat 66 – Diagnosis & Management of Vaginal Discharge

📌 For assistance or more information, contact your local Ampath representative or clinical pathologist.