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

Sexual health is important for wellbeing and reproductive health, and includes the prevention, screening, diagnosis, and treatment of urogenital infections in women. However, ensuring that sexual healthcare is truly comprehensive remains a topic of concern for women and their healthcare providers alike. Understanding 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 repeatedly 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. Furthermore, 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 commonly used? As lab professionals, we have a role in contributing to more accurate 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 detection 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 sensitivity 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 vaginal swabs were considered the preferred noninvasive sample type by these investigators.8 In a survey of opinions on ease and preferences for sampling of over 1,000 women across seven North American cities, women preferred self-collected vaginal swabs over urine or cervical swab collection during a pelvic exam.9 The vast majority found vaginal swabs easy to use and agreed they would get tested more regularly if self-collected swabs were an option. Self-collected vaginal swabs were preferred by the majority of college women undergoing STI testing in another survey in upstate New York.10 Availability of this option might increase testing overall because self-obtained vaginal swabs are a quick, easy way to test for STIs without a pelvic exam, helping those women who avoid STI testing due to anxiety and discomfort, or when access to a healthcare provider is not possible.

Self-collected vaginal swabs are more sensitive, less messy, less susceptible to laboratory errors, less expensive, and more cost-effective than urine testing. Finally, the Centers for Disease Control and Prevention (CDC) recommends either clinician- or self-collected vaginal swabs for CT and NG testing; self-collected vaginal swabs are considered equivalent in sensitivity and specificity to those collected by a clinician.11 Self-collected vaginal swabs have been estimated in mathematical modeling as the most cost-effective sampling method for prevention of pelvic inflammatory disease, which suggests benefits to the clinical care providers.12 Additionally, as more point-of-care tests become available, self-collection of swabs immediately following registration has been shown to decrease the wait time for results and improve clinic throughput.13 Regardless of whether the testing will be done on site or sent to a laboratory, self-collection prior to the exam frees up time to allow providers to engage in other activities with their patients.

Beyond CT/NG testing

Along with the advantages mentioned above, vaginal swab samples allow the opportunity to test for a broader range of organisms from a single sample compared with urine. This is particularly important for symptomatic patients, as many STI and vaginitis symptoms overlap. For example, symptomatic MG infections present similarly to CT, NG, and TV infections, so all tests should be performed.14 Additionally, co-infections with MG and other bacterial STIs have frequently been reported.15, 16, 17 With these scenarios in mind, healthcare providers must look beyond CT and NG and consider testing women for other genital pathogens, such as MG, TV, or those underlying pathogens causing bacterial vaginitis (BV), to determine the most appropriate treatment/s and reduce return visits. For MG and vaginitis, urine has been clearly demonstrated to be a sub-optimal sample type.

Heeding the latest professional guidance

The CDC recently released updated STI treatment guidelines to provide guidance for diagnosing and treating infections like TV, BV, and MG. These recommendations further demonstrate the importance of testing for common pathogens beyond CT and NG.

TV is estimated to be the most prevalent nonviral STI worldwide, affecting approximately 3.7 million people in the United States.14 The CDC had previously recommended diagnostic testing for TV in women seeking care for vaginal discharge. Annual screening should be considered for those in high prevalence settings, such as STI clinics, correctional facilities, and for high-risk asymptomatic women with a history of STIs or incarceration, multiple sex partners, transactional sex, and other identified factors. Asymptomatic women with HIV should be routinely annually screened for TV. Due to a high rate of reinfection, TV retesting within three months of treatment is recommended for sexually active women. Nucleic acid amplification tests (NAATs) for TV were also noted to be more sensitive than wet mount microscopy and culture; both vaginal swabs and urine are considered acceptable samples. The updated recommended treatment regimen for women is 500 g metronidazole orally twice daily for 7 days.14

BV is the most common cause of vaginal discharge worldwide, although most women are asymptomatic.14 Traditional methods of diagnosis such as Amsel’s diagnostic criteria or gram stain are commonly used, although more accurate and sensitive NAATs are available. The CDC recommends that symptomatic women should be tested for BV with NAATs using vaginal swab samples, and all women with BV should also be tested for HIV and other STIs. Use of vaginal swabs supports this multi-test approach.

MG is another common infection that is difficult to culture and has a low organism load. Infection with MG doubles the risk of cervicitis, pelvic inflammatory disease (PID), preterm delivery, and spontaneous abortion.14 MG prevalence is also surprisingly high. Among young adults in the general US population, MG (1%) is more common than NG (0.4%) and less common than CT (2.3%).15 In a study of 515 women seeking healthcare at family medicine, obstetrics and gynecology, family planning, public health, or sexually transmitted disease clinics in the US, MG infections were significantly more prevalent than CT and NG infections, and over 50% of women with MG infections had the macrolide-resistant phenotype.16 Among 1,737 sexually active women seeking healthcare at 21 U.S. sites that included clinical research centers, emergency medicine, family planning, public health, STI, and family medicine/obstetric-gynecologic facilities, 10.1% were infected with M. gen; prevalence was lowest (7.9%) in endocervical and urine samples from asymptomatic women and highest (11.6%) in urine samples and patient-collected vaginal specimens from symptomatic women.18 Overall, MG is more prevalent in younger, black, non-Hispanic, and symptomatic women.16,18,19

The recent CDC guidelines recommend that women with recurrent cervicitis be tested for MG using NAATs.14 In Europe, testing is recommended for cervicitis even if it is not a recurrence. Testing for MG should be considered for women with pelvic inflammatory disease. Vaginal swabs are also the specimen of choice for testing for MG.15, 20 Additionally, due to the increasing resistance of MG to azithromycin, the CDC recommends that any MG patient undergo antimicrobial resistance testing, when available, to guide appropriate treatment.14

Reframing practice patterns to improve women’s sexual health

Vaginal swabs are an easy, patient-preferred sample type that allows for self-collection and detection of a broad range of pathogens, yet does not sacrifice clinical performance, with sensitivity equal to or better than other sample types. In the past, urine may have been considered a better alternative to endocervical swabs for women, but we now have the best of both worlds — usability and performance — with the vaginal swab. Importantly, detecting multiple pathogens better addresses the needs of symptomatic women, as symptoms from many STIs overlap, and coinfections are not uncommon. CDC recommended treatments are pathogen-specific; therefore, receiving an accurate diagnosis will ensure proper treatment is given, reducing return visits and supporting antibiotic stewardship programs. Women deserve more comprehensive, efficient, and effective sexual health care that includes testing with a superior sample type — the vaginal swab.


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