BACKGROUND AND PURPOSE:

• Vaginal swabs are recommended for detection of chlamydia, gonorrhea, and/or trichomoniasis, but many commercially available kits use urine samples
• Aaron et al. (Ann Fam Med, 2023) assessed the diagnostic sensitivity of commercially available assays for vaginal swabs vs urine specimens from women

METHODS:

• Systematic review and meta-analysis
• Study inclusion criteria
  • Studies that evaluated commercially available STI assays
  • Data obtained from the same assay on both a urine specimen and a vaginal swab from the same patient
• Study design
  • Pooled estimates of sensitivity were calculated, as well as odds ratios for any difference in performance
• Primary outcome
  • Sensitivity of tests for detecting chlamydia, gonorrhea, and trichomoniasis

RESULTS:

• 28 articles
  • Comparisons for chlamydia: 30 | Gonorrhea: 16 | Trichomoniasis: 9
• Pooled sensitivity estimates were higher for vaginal swabs for all infections (P<0.001 for all)
  • Chlamydia
    • Vaginal swabs: 94.1% (95% CI, 93.2% to 94.9%) | Urine samples: 86.9% (95% CI, 85.6% to 88.0%) 
    • Odds ratio (OR) that vaginal swabs were more sensitive than urine for detection: 2.69 (95% CI, 2.21 to 3.28); P<.001
  • Gonorrhea
    • Vaginal swabs: 96.5% (95% CI, 94.8% to 97.7%) | Urine samples: 90.7% (95% CI, 88.4% to 92.5%) 
    • OR that vaginal swabs were more sensitive than urine for detection: 3.68 (95% CI, 2.19 to 6.18); P<.001
  • Trichomoniasis
    • Vaginal swabs: 98.0% (95% CI, 97.0% to 98.7%) | Urine samples: 95.1% (95% CI, 93.6% to 96.3%) 
    • The difference in sensitivity was not statistically significant: OR of 2.48 (95% CI, 1.50 to 4.08); P=0.15

CONCLUSION:

• Compared to urine samples, vaginal swabs have superior sensitivity for detecting chlamydia and gonorrhea
• There was a small sample size for trichomoniasis
• The authors state

For female screening, the CDC has recommended vaginal swabs as the optimal specimen type for both CT and NG NAATs since 2014

Our data support and reinforce that recommendation by adding analyses of numerous publications since the evidence for the CDC recommendations was generated

We cannot continue to justify the use of urine except for women for whom collection of a vaginal sample is not acceptable

Learn More – Primary Sources:

Vaginal Swab vs Urine for Detection of Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis: A Meta-Analysis