Evaluation of the Hologic Aptima Vaginitis assays for microbiological diagnosis of vaginitis in women with abnormal vaginal discharge attending primary care

Introduction. Infectious vaginitis, caused mostly by bacterial vaginosis (BV), Candida vaginitis (CV) and Trichomonas vaginitis (TV), is a common reason for primary care visits. Recent studies demonstrate the potential utility of molecular assays in replacing conventional diagnostic methods. Hypothesis/Gap Statement. Different diagnostic standards are in use for BV; published studies have evaluated molecular diagnostic tests against Amsel criteria, Nugent score or a combination of both. In the UK, Hay/Ison criteria are commonly used, but there are limited studies evaluating molecular diagnostic assays against these criteria. Aim. This study evaluated the performance of Hologic’s Aptima® BV and CV/TV assays relative to Hay/Ison criteria for BV and culture for CV in women with symptoms of vaginitis attending primary care centres in the UK. Methodology. Paired vaginal swabs were collected from women ≥18 years of age undergoing testing for Chlamydia trachomatis and Neisseria gonorrhoea using the Hologic Aptima Combo 2 (AC2) assay, alongside standard of care (SOC) testing for vaginitis (Hay/Ison criteria for BV; culture for CV). Samples received for AC2 testing were tested for vaginitis using Hologic Aptima BV and Aptima CV/TV assays. Sensitivity, specificity, positive and negative predictive values and diagnostic accuracy of Aptima BV and Aptima CV/TV assays relative to SOC methodology were determined. For discrepancy analysis, selected samples were evaluated further using third-party (Thermo Fisher) Vaginal Plus and pan-Candida real-time PCR. Results. This study included 2,152 women. The mean (standard deviation) age of participants was 35.1 (11.5) years. Sensitivity and specificity estimates for the Aptima BV assay were 98.8% and 77.7% and 94.9% and 88.3% for CV detection by Aptima CV/TV, respectively, relative to SOC. Overall diagnostic accuracy values were 80.2% for Aptima BV and 90.0% for Aptima CV/TV. Although not routinely tested for in our population, a limited evaluation of TV detection by the combined Aptima CV/TV assay relative to the monoplex Aptima TV assay in 75 women indicated sensitivity and specificity values of 87.5% and 100%, respectively. Conclusion. The Aptima BV and CV/TV assays demonstrated high sensitivity and specificity relative to SOC methodology in UK laboratories and are a viable alternative to conventional vaginitis testing.