What labs should be ordered for a patient with suspected chlamydia and gonorrhea?

Laboratory Testing for Suspected Chlamydia and Gonorrhea

For patients with suspected chlamydia and gonorrhea, nucleic acid amplification tests (NAATs) should be ordered using appropriate specimens based on the patient's sexual practices and exposure sites.

Recommended Testing Approach

Primary Diagnostic Tests

• Nucleic acid amplification tests (NAATs) are the gold standard for diagnosing both chlamydia and gonorrhea due to their high sensitivity (>95%) and specificity (>97%) 1, 2

Specimen Collection Based on Exposure Sites

1. For all patients:

   • Urine specimen - First-catch urine (first part of the urinary stream) is appropriate for both males and females 1

2. For females:

   • Vaginal swabs (clinician-collected or self-collected) - Preferred specimen with equivalent performance to cervical specimens 1, 3
   • Endocervical swabs - If pelvic examination is being performed 1

3. For males:

   • Urethral swabs - Particularly if symptomatic with urethral discharge 1

4. For patients reporting receptive oral sex:

   • Pharyngeal swabs - Culture is traditionally recommended, though some labs have validated NAATs for this site 1

5. For patients reporting receptive anal sex:

   • Rectal swabs - Culture is traditionally recommended, though some labs have validated NAATs for this site 1

Additional Testing Considerations

Co-testing for Other STIs

All patients being tested for chlamydia and gonorrhea should also be tested for:

• Syphilis (serology)
• HIV (serology) 1, 2

Special Situations

• Persistent infection after treatment: Both culture and antimicrobial susceptibility testing should be performed, especially for gonorrhea 1

• Asymptomatic screening: NAATs on urine or self-collected vaginal swabs are appropriate and increase testing accessibility 4, 5

Clinical Pearls and Pitfalls

• Do not rely on symptoms alone for diagnosis - 53-100% of extragenital infections and many genital infections are asymptomatic 2, 5

• Gram stain limitations: While Gram stain of urethral discharge in symptomatic men showing polymorphonuclear leukocytes with intracellular Gram-negative diplococci can suggest gonorrhea, it is not sufficient for ruling out infection in asymptomatic men 1

• Specimen type considerations:

  • Vaginal specimens have similar performance to cervical specimens but higher acceptability and lower cost 3
  • Self-collected specimens enable screening outside traditional clinical settings 4

• Test of cure: Generally not recommended except in special circumstances (e.g., persistent symptoms, suspected reinfection, or pregnancy)

• Laboratory requisition forms: Ensure the laboratory knows which anatomical sites are being tested, as different processing may be required

By following these evidence-based testing recommendations, clinicians can accurately diagnose chlamydia and gonorrhea infections, leading to appropriate treatment and reduced risk of complications including pelvic inflammatory disease, infertility, and increased HIV transmission risk.