C-162. The Affirm™ VPIII Test Classifies More Subjects Positive for Gardnerella vaginalis and Fewer Positive for Candida sp. than Culture
Background: The Affirm™ VPIII test uses DNA probes to detect nucleic acid from Candida species (CS), Gardnerella vaginalis (GV) and Trichomonas vaginalis for the diagnosis of vaginitis/vaginosis. Following validation and implementation of this test, we observed a high positivity rate for GV in clinical samples. Therefore, we undertook this study to compare the performance of Affirm™ VPIII for GV and CS with culture. Methods: Sixty-nine volunteer subjects were recruited from the workplace. Subjects self-collected multiple vaginal swabs in random order using the Ambient Temperature Transport System (ATTS). Symptoms were not assessed or reported. Affirm™ VPIII (Becton, Dickinson and Co.) testing was performed immediately on one ATTS according to manufacturer’s instructions; additional ATTS were tested 24 and 72 h post collection. To simulate transit, a culture swab was used to inoculate a 5% sheep blood plate for general vaginal culture, a V-agar plate for GV culture and a SAB-HI with gentamicin plate for CS culture 24 h post collection. Standard laboratory techniques were used to identify GV and CS.Results: Ten subjects were positive for GV by culture and Affirm™ VPIII at all time points. Twenty-nine additional subjects were positive for GV by Affirm™ VPIII at ≥1 time point but had negative GV culture. Uninoculated ATTS gave false positive GV Affirm™ VPIII results. Eight subjects had moderate or heavy growth of CS; 4/8 had positive Candida Affirm™ VPIII results at ≥1 time point. Of 10 subjects with light to rare CS growth and 51 subjects with no growth of CS in culture, no positive Candida Affirm™ VPIII results were obtained. Conclusions: Using culture results as the gold standard in this population of volunteers with unknown symptom status, Affirm™ VPIII demonstrated 100% sensitivity but poor specificity for GV; 74% of positive GV Affirm™ VPIII subjects failed to confirm by culture. Conversely, for CS, Affirm™ VPIII was less sensitive than culture, detecting CS in 50% of subjects with moderate or heavy growth of CS in culture. Affirm™ VPIII classifies more subjects positive for GV and fewer subjects positive for Candida sp. than culture.