What is the preferred sampling method for gonorrhea testing, urethral swab or urine test, in a patient with suspected gonorrhea?

Gonorrhea Testing: Urethral Swab vs Urine Specimen

Both urethral swabs and urine specimens are acceptable for gonorrhea testing using nucleic acid amplification tests (NAATs), with the choice depending on clinical context—urethral swabs are preferred when culture is needed for antimicrobial susceptibility testing or when discharge is present, while urine testing offers a non-invasive alternative with comparable sensitivity for screening purposes. 1

Specimen Selection Based on Clinical Scenario

For Symptomatic Men

• Urethral swabs are the traditional standard when urethral discharge is present, particularly if Gram stain is being performed for point-of-care diagnosis (>95% sensitivity and >99% specificity for symptomatic men) 1
• Delay specimen collection until at least 2 hours after the patient has voided 2
• Insert the swab 2-4 cm into the urethra and rotate in one direction for at least one revolution for 5 seconds 2
• Meatal swabs should be avoided in the absence of visible discharge as they are associated with a 45% Gram stain failure rate compared to 3% for urethral swabs due to insufficient cellular material 3

For Asymptomatic Men (Screening)

• Urine NAATs are FDA-cleared and highly effective for screening asymptomatic men, with sensitivity of 88-92% and specificity of 99% 1, 4
• Urine testing eliminates the discomfort of urethral swabbing, improving patient acceptance for screening programs 5, 4
• First-void urine is the optimal specimen type for male patients 2

When Culture is Required

• Urethral swabs are mandatory when culture is needed, as culture and nucleic acid hybridization tests require male urethral swab specimens 1
• Culture is essential in cases of persistent gonococcal infection after treatment to obtain antimicrobial susceptibility results 1
• Culture from urethral swabs can isolate viable N. gonorrhoeae even in asymptomatic men who screen positive by urine NAAT (76% culture-positive rate) 6

NAAT Platform Considerations

• NAATs offer the widest range of testing specimen types and are FDA-cleared for use with male urethral swabs and male urine 1
• Product inserts for each NAAT vendor must be carefully examined as FDA-cleared specimen types vary by manufacturer 1
• Use the swab supplied or specified by the manufacturer, as different platforms have specific requirements 7, 2

Critical Technical Points

Urethral Swab Collection

• The objective is to obtain columnar epithelial cells from the urethral mucosa, not just secretions or discharge 7, 2
• Without quality assurance, >10% of specimens will be unsatisfactory, containing only secretions without adequate cellular material 2
• Withdraw the swab carefully without touching external surfaces 2

Urine Collection

• First-void urine provides optimal sensitivity for NAAT testing in males 2
• Urine samples can be left at room temperature for several days, allowing for mail-in home-based testing programs 4

Common Pitfalls to Avoid

• Do not use meatal swabs for Gram stain testing when discharge is absent—they contain significantly less cellular material and result in poor-quality smears 3
• Do not rely on Gram stain alone for asymptomatic men—negative Gram stains have lower sensitivity and should not rule out infection 1
• Do not collect urethral specimens too soon after voiding—wait at least 2 hours to ensure adequate organism concentration 2
• Do not use nonculture tests when antimicrobial susceptibility testing is needed—culture is required to guide therapy in treatment failures 1

Special Considerations for Surveillance

• Clinicians should consider performing urethral culture in asymptomatic men who screen positive by urine NAAT to ensure optimal surveillance for antimicrobial resistance, as viable organisms can be isolated in 60-90% of such cases 6
• Culture provides critical epidemiologic data on resistance patterns that NAATs cannot provide 1