Vaginal swabs are superior to urine samples in detecting sexually transmitted infections (STIs) such as chlamydia, trichomoniasis and gonorrhea, according to new research published in the March-April 2023 issue of the Annals of Family Medicine.¹

After screening 313 studies from 1995 through 2021, 28 were included in the final meta-analysis. These studies included both symptomatic and asymptomatic women attending STD, Obstetrics and Gynecology and/or family planning clinics.

Analysis showed that the pooled sensitivity for vaginal swabs was 94.1% for chlamydia, 96.5% for gonorrhea and 98% for trichomoniasis, whereas the sensitivity of urine samples for chlamydia was 86.9%, 90.7% for gonorrhea and 95.1% for trichomoniasis. Vaginal swabs were 2.69-times more likely to yield a diagnosis of chlamydia trachomatis compared to urine specimens with odds ratio (OR) of 2.69. The sensitivity of vaginal swabs in detecting Neisseria gonorrhoeae was higher than urine samples with OR of 3.68. However, no difference was noted between the two sample types in their sensitivity in detecting Trichomonas vaginalis (OR 2.48).

The Centers for Disease Control and Prevention (CDC) recommends vaginal swabs as the preferred specimens when testing for chlamydia, gonorrhea and/or trichomoniasis. However, there are barriers such as physician hesitancy that preclude the use of vaginal swabs. The findings of this study corroborate this recommendation. The diagnostic sensitivity of vaginal swabs was significantly higher for detection of chlamydia and gonorrhea vs urine specimens, though the difference in sensitivity between the two in diagnosing trichomoniasis was nonsignificant. The authors suggest that either “self-collected or provider-collected” vaginal swabs may be used for screening and urine samples should be obtained only from those women “for whom collection of a vaginal sample is not acceptable”. 

Reference

1. Aaron KJ, et al. Vaginal swab vs urine for detection of chlamydia trachomatis, neisseria gonorrhoeae, and trichomonas vaginalis: a meta-analysis. Ann Fam Med. 2023 Mar-Apr;21(2):172-179. doi: 10.1370/afm.2942.