Nucleic Acid Amplification Testing Compared With Cultures, Gram Stain, and Microscopy in the Diagnosis of Vaginitis

The aim of the study was to evaluate the performance of nucleic acid amplification testing (NAAT) for the diagnosis of vulvovaginal candidiasis (VVC), bacterial vaginosis, and Trichomonas vaginalis.

A cross-sectional analysis of women with (n = 200) and without (n = 100) vulvovaginal symptoms was enrolled from outpatient gynecology offices and a vulvovaginal referral clinic. Vaginal swabs were analyzed by wet mount microscopy, yeast culture, Gram stain, T. vaginalis culture, and NAAT. Sensitivity and specificity analyses were performed.

Among symptomatic women, the sensitivity of microscopy was 48.5% for VVC and 75% for T. vaginalis. Sensitivities of NAAT and culture for diagnosing VVC were 92.4% and 83.3%, respectively, whereas these methods were 100% and 93.8% for T. vaginalis. The sensitivity for bacterial vaginosis diagnosis by clinical criteria ("Amsel criteria"), Gram stain, and NAAT were 98.7%, 82.7%, and 78.7%, respectively. Test concordance rates were high between culture and NAAT for Candida species (91%) and between Gram stain and NAAT for the detection of bacterial vaginosis (88%). Among asymptomatic women, 20%-21% tested positive for bacterial vaginosis by Gram stain or NAAT, and 8%-13% were colonized with Candida species based on culture or NAAT.

Given the limitations of wet mount sensitivity for VVC and T. vaginalis, culture or NAAT testing should be considered when evaluating women with symptoms of vaginitis who test negative by microscopy. Although Amsel criteria accurately diagnosed bacterial vaginosis, NAAT is preferred for detection of T. vaginalis and performed similarly to culture for the diagnosis of VVC.