INFECTION DIAGNOSTICS :: STIs


Some studies show that vaginal swabs are more accurate than urine samples in detecting STIs, such as those caused by Mycoplasma genitalium bacteria, which is pictured here.


The role of the vaginal swab in providing comprehensive sexual healthcare for women


By Barbara Van Der Pol, PHD, MPH S


exual health is important for well- being and reproductive health, and includes the prevention, screening,


diagnosis, and treatment of urogenital in- fections in women. However, ensuring that sexual healthcare is truly comprehensive remains a topic of concern for women and their healthcare providers alike. Under- standing of best practices differs greatly across providers, and there is a need to update testing practices to provide more comprehensive, accurate, and efficient care. When testing women for sexually


transmitted infections (STIs) or vaginal infections, vaginal swabs have been re- peatedly shown to produce more accurate diagnoses for STIs.1, 2, 3, 4, 5


Yet testing urine


for evidence of urogenital infections in women is still common practice. Data on the superior performance of vaginal swabs has been shown in many studies. Further- more, the vaginal swab offers a broader range of pathogen detection than urine, which more appropriately addresses the clinical needs of symptomatic women. So why aren’t vaginal swabs being more com- monly used? As lab professionals, we have a role in contributing to more accurate


18 DECEMBER 2021 MLO-ONLINE.COM


and holistic testing for sexual health by educating and urging healthcare providers to provide comprehensive testing using superior sample types.


Sample type matters Vaginal swabs have been shown to be superior to urine specimens for detec- tion of STIs across different diagnostic assays in multiple studies for more than a decade. A study comparing clinician- and patient-collected vaginal swabs and urine samples for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) testing found more infections with swabs than urine samples from the same patients.1 Likewise, a head-to-head comparison found more CT and NG infections with vaginal swabs than with the urine samples.2


Sensitivities were equivalent for


endocervical specimens and self-collected vaginal swabs in a study of CT-infected women; however, the sensitivity for urine samples was significantly lower.6


In yet


another study, clinician- or self-collected vaginal swabs yielded higher sensitivity for both CT and NG than urine samples from the same women.4


This trend holds


for infections other than CT and NG. A study of more than a thousand women tested for simultaneous detection of CT, NG, and Trichomonas vaginalis (TV) found that swabs yielded a higher sen- sitivity for CT and TV than urine samples. NG was similar between sample types, and both sample types had similar high specificities.3


Another study showed that


vaginal swabs had the highest sensitivity while urine had the lowest for detection of NG, CT, TV, Mycoplasma genitalium (MG), and human papillomavirus.5


Vaginal swabs: self-collection is possible, effective, and preferred Like urine, vaginal swabs can be self- collected. In 2006, an NIH-sponsored workshop concluded that self-obtained vaginal swabs were the optimal specimen type for CT/NG testing and that testing for other pathogens with self-obtained vaginal swabs should be explored.7


In a


study of CT-infected women, endocervical and self-collected vaginal swabs yielded higher organism loads than urine, with urine specimens yielding the 15-50 times lower load than swabs; thus, self-collected


Courtesy of CDC.


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