Prospective Evaluation of Molecular Assays for Diagnosis of Vaginitis

Molecular tests to diagnose conditions involving the disruption of normal microbiota are difficult to optimize. Using Nugent-scored Gram stain (NS) as the reference standard, we evaluated the performance of 3 molecular assays for the diagnosis of bacterial vaginosis (BV) and examined the impact of an incremental increase in bacterial targets. The BD Affirm assay includes a DNA probe for Gardnerella vaginalis, the Hologic transcription-mediated amplification (TMA) analyte-specific reagent (ASR) assay adds a second Lactobacillus sp. target, and the recently cleared in vitro diagnostic use (IVD) Aptima BV assay includes a third target (Atopobium vaginae). The diagnosis of vulvovaginal candidiasis (VVC) by the Affirm and Candida vaginitis Hologic TMA ASR assays was assessed using microscopy for yeast as the reference standard. From May to December 2018, 111 women with vaginitis symptoms prompting the clinician to order an Affirm test were enrolled with informed consent for the collection of additional specimens. Clinicians accurately predicted BV as the most likely diagnosis for 71% of the 45 patients with BV. Coinfection occurred in 13.5% of patients. For BV, the specificity of the Aptima IVD assay (86.3%) was higher than the Affirm assay (60.6%, P = 0.0002), but sensitivities were not significantly different. For VVC, the sensitivity of the ASR assay (100%) was higher than Affirm (75.9%; P = 0.023) and the specificity of the Affirm assay (98.8%) was higher than the ASR assay (86.6%; P = 0.004).