Can the same swab be used for sexually transmitted infection (STI) testing of the urethra and anus?

From the Guidelines

No, you should not use the same swab for STI testing of both the urethra and anus. According to the most recent and highest quality study, 1, nucleic acid amplification tests (NAATs) are the recommended method for diagnosing chlamydia and gonorrhea, and these tests have high sensitivity and specificity for urogenital sites, including male and female urine, as well as clinician-collected endocervical, vaginal, and male urethral specimens. However, rectal and pharyngeal swabs can be collected from persons who engage in receptive anal intercourse and oral sex, although these collection sites have not been cleared by the U.S. Food and Drug Administration.

Using the same swab for both urethral and anal testing could lead to cross-contamination, which may result in false positive results or missed infections. The study 1 emphasizes the importance of using NAATs for diagnosis, but it does not explicitly address the use of the same swab for multiple sites. However, based on the principles of preventing cross-contamination and ensuring accurate test results, it is recommended to use separate swabs for each anatomical site.

Some key points to consider when collecting samples for STI testing include:

• Using separate, sterile swabs for each anatomical site to prevent cross-contamination
• Following the manufacturer's instructions for the specific testing kit being used
• Ensuring that the healthcare provider or individual collecting the samples is properly trained and follows proper protocols
• Being aware of the potential risks of cross-contamination and the importance of accurate test results for proper diagnosis and treatment.

In addition, the study 2 provides guidance on the diagnosis and treatment of chlamydia and gonorrhea, but it does not provide information on the use of the same swab for multiple sites. However, it emphasizes the importance of using NAATs for diagnosis and following proper protocols for sample collection and testing. In summary, using separate swabs for each anatomical site is the recommended approach to prevent cross-contamination and ensure accurate test results.

From the Research

STI Testing with the Same Swab

• The use of the same swab for STI testing with urethra and anus is not explicitly recommended in the provided studies 3, 4, 5, 6, 7.
• However, the study by 3 compares self-collected vaginal, urine, pharyngeal, and rectal samples to clinician-collected cervical, urethral, pharyngeal, and rectal sampling techniques, suggesting that different sampling methods can be used for STI testing.
• The study by 3 also recommends that guidelines on how to self-collect gonorrhea and chlamydia urine, vaginal, rectal, and pharyngeal specimens be published, implying that separate swabs may be necessary for different sampling sites.
• There is no direct evidence to support the use of the same swab for both urethra and anus STI testing, and it is unclear whether this practice would be effective or safe.

Sampling Methods for STI Testing

• The study by 3 found that self-collected urine samples compared to clinician-collected urethra samples in males produced a sensitivity of 88% and a specificity of 99% for chlamydia testing.
• The same study found that self-collected urine samples compared to clinician-collected urethra samples in males produced a sensitivity of 92% and a specificity of 99% for gonorrhea testing.
• The study by 6 mentions that fast, sensitive molecular diagnostic tests that use urine or self-collected swabs may lead to more screening opportunities and be more acceptable to patients.

Treatment and Guidelines

• The study by 4 updates the CDC's treatment guidelines for gonococcal infection, recommending a single 500 mg IM dose of ceftriaxone for treatment of uncomplicated urogenital, anorectal, and pharyngeal gonorrhea.
• The study by 5 provides updated, evidence-based testing and treatment recommendations for STIs, including the use of ceftriaxone monotherapy for gonorrhea and doxycycline for chlamydia.
• The study by 7 summarizes the 2021 CDC guidelines on sexually transmitted infections, recommending a higher dose of ceftriaxone for gonorrhea and doxycycline as first-line therapy for chlamydia.