Table 2. NAATs for Vaginitis [return to contents]

Table 3. Other Laboratory Tests for Vaginitis [return to contents]

Test selection and interpretation [return to contents]

According to ACOG and CDC guidelines, symptomatic patients should be tested for BV, VC, and trichomoniasis.^1,3 Sexually active patients may be tested for STIs such as Chlamydia trachomatis and Neisseria gonorrhoeae, as 18% of women with vaginitis also have STIs.^2,6 More information about STI testing can be found in the related guide, Sexually Transmitted Infections Associated With Urethritis, Cervicitis, and Pelvic Inflammatory Disease: Laboratory Testing for Screening, Diagnosis, and Management. Although vaginal infections can be asymptomatic, guidelines do not recommend testing for BV and VC in asymptomatic patients.^1,3 However, screening for trichomoniasis is recommended annually for women with HIV and can be considered for women at high risk for infection.¹

Laboratory tests for vaginitis include molecular tests, such as NAATs and DNA probe tests, and culture. According to guidelines, NAATs can be used to test for all 3 common causes of vaginitis.^1,3 Advantages of NAATs include their high sensitivity and specificity (Table 4),^5,8 ability to test for multiple infections using the same swab, and ability to use clinician- or patient-collected swabs.⁶ Quest offers SureSwab^® transcription-mediated amplification NAATs that can test for single or multiple infections, including STIs (Table 2). DNA probe tests (Bacterial Vaginosis/Vaginitis Panel, test code 14577) can also detect all 3 common causes of vaginitis but have lower sensitivity and specificity than NAATs (Table 4). Culture can be used to identify Candida species in VC and to determine drug susceptibilities in VC and trichomoniasis.^1,3

Table 4. Sensitivity and Specificity of Molecular Tests for Common Causes of Vaginitis [return to contents]

Laboratory testing options specific to each infection are discussed in the following sections.

Bacterial vaginosis

According to guidelines, molecular tests such as NAATs and DNA probe tests can be used to detect BV.^1,3 Quest's BV NAATs (Table 2) measure the relative abundance of bacterial species associated with BV (Gardnerella vaginalis and Atopobium vaginae) and species negatively associated with BV (Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus jensenii).⁹ An algorithm then determines whether the vaginal flora detected is consistent (positive result) or inconsistent (negative result) with BV. DNA probe testing for G vaginalis (included in the Bacterial Vaginosis/Vaginitis Panel, test code 14577) has lower specificity than NAAT for detecting BV (Table 4) because it only tests for the presence of a single organism.¹⁰

Because the BV NAATs offered by Quest are based on the microbiome of reproductive-aged patients, they may not be accurate in premenarchal patients, and due to regulatory restrictions, cannot be used for patients under 14 years of age.⁹ Alternative test selection depends on whether the patient has entered puberty. For pubescent patients under 14 who have signs and symptoms of BV, a DNA probe test (test code 14577) can be used. In prepubescent patients, vulvovaginitis commonly results from noninfectious causes (eg, poor hygiene or irritants), and diagnostic testing may not be necessary. However, if symptoms persist after such factors have been addressed, vaginal culture to test for respiratory and enteric bacteria (test code 4558) may be appropriate.¹¹

Because normal vaginal flora varies between individuals, test results should be considered together with clinical evaluation to diagnose or rule out BV.^9,10 Guidelines recommend that women with BV be tested for HIV and other STIs.¹

Vulvovaginal candidiasis

Test selection for VC may depend on whether the infection is classified as complicated (10%-20% of cases¹) or uncomplicated. Complicated infections, which require more intense treatment, are those involving recurrent or severe symptoms, non–C albicans infections (suspected or confirmed), or patients with diabetes or immunocompromising conditions.^1,3 According to guidelines, complicated infections should be evaluated by culture (test codes 20541 and 36268), which allows for species identification and susceptibility testing.^1,3 As identification by culture can take up to 1 week, Quest also offers culture testing options that include phenotypic direct fluorescent microscopic evaluation (test codes 3968 and 36270), a faster but less sensitive method that provides preliminary results in 1 to 2 days while culture results are pending.

For uncomplicated infections, which do not require species identification, molecular tests can be used to detect Candida.^1,3 Quest's NAATs detect and report separate results for (1) Candida species group (C albicans, C dubliniensis, C parapsilosis, C tropicalis), and (2) C glabrata, which is often resistant to azoles and has different treatment recommendations.^1,3,12 Quest's DNA probe test for Candida (included in the Bacterial Vaginosis/Vaginitis Panel, test code 14577) detects C albicans, C glabrata, C kefyr, C krusei, C parapsilosis, and C tropicalis.¹⁰

Regardless of the method used, detection of Candida is consistent with VC in symptomatic women. However, Candida is present in the normal vaginal flora of 10% to 20% of women.¹

Trichomoniasis

According to guidelines, NAATs are recommended to detect Trichomonas vaginalis because of their high sensitivity and specificity.^1,3 DNA probe tests (included in the Bacterial Vaginosis/Vaginitis Panel, test code 14577), can also be used to detect T vaginalis but have lower sensitivity than NAAT (Table 4).

Results from these tests indicate whether T vaginalis nucleic acid was detected (consistent with trichomoniasis) or not detected (consistent with absence of trichomoniasis).^10,12 According to guidelines, women with trichomoniasis should be tested for HIV, syphilis, and other STIs and should be retested for T vaginalis within 3 months of treatment.^1,3