Diagnostic Performance of a Molecular Test versus Clinician Assessment of Vaginitis

Abstract

Vaginitis is a common complaint, diagnosed either empirically or using Amsel's criteria and wet mount microscopy. This study sought to determine characteristics of an investigational test (a molecular test for vaginitis), compared to reference, for detection of bacterial vaginosis, Candida spp., and Trichomonas vaginalis Vaginal specimens from a cross-sectional study were obtained from 1,740 women (≥18 years old), with vaginitis symptoms, during routine clinic visits (across 10 sites in the United States). Specimens were analyzed using a commercial PCR/fluorogenic probe-based investigational test that detects bacterial vaginosis, Candida spp., and Trichomonas vaginalis Clinician diagnosis and in-clinic testing (Amsel's test, potassium hydroxide preparation, and wet mount) were also employed to detect the three vaginitis causes. All testing methods were compared to the respective reference methods (Nugent Gram stain for bacterial vaginosis, detection of the Candida gene its2, and Trichomonas vaginalis culture). The investigational test, clinician diagnosis, and in-clinic testing were compared to reference methods for bacterial vaginosis, Candida spp., and Trichomonas vaginalis The investigational test resulted in significantly higher sensitivity and negative predictive value than clinician diagnosis or in-clinic testing. In addition, the investigational test showed a statistically higher overall percent agreement with each of the three reference methods than did clinician diagnosis or in-clinic testing. The investigational test showed significantly higher sensitivity for detecting vaginitis, involving more than one cause, than did clinician diagnosis. Taken together, these results suggest that a molecular investigational test can facilitate accurate detection of vaginitis.

Keywords: Amsel's test; Nugent score; bacterial vaginosis; candidiasis; clinician diagnosis; diagnostic accuracy; molecular test; sensitivity; specificity; trichomoniasis; vaginitis; wet mount microscopy.

FIG 1

Evaluable specimens included in this study. Top left, eligible participants; bottom left, evaluable specimens for bacterial vaginosis; top right, evaluable specimens for Candida species; bottom right, evaluable specimens for Trichomonas vaginalis. Abbreviations: w/o, without; BV, bacterial vaginosis; CS, Candida species; TV, Trichomonas vaginalis; RM, reference method; INV, investigational, NuSc, Nugent score; AmC, Amsel's criteria; KOH, potassium hydroxide preparation.

FIG 2

Sensitivity of diagnostic methods for detection of one or multiple causes of vaginitis. (Top) The sensitivity values (percent) for in-clinic testing, clinician diagnosis, and the investigational test are shown for bacterial vaginosis, Candida spp., and Trichomonas vaginalis. (Bottom) The sensitivity values (percent) for clinician diagnosis and the investigational test are shown for vaginitis cases involving more than one cause. Abbreviations: BV, bacterial vaginosis; CS, Candida spp.; TV, Trichomonas vaginalis; IC, in-clinic testing; CD, clinician diagnosis; INV, PCR-based molecular, investigational test. †, P < 0.0001; ‡, P < 0.0005.

FIG 3

Test accuracy as a function of increasing prevalence of vaginitis cause. The three panels represent bacterial vaginosis (A), Candida spp. (B), and Trichomonas vaginalis (C). Change in test accuracy is plotted (y axis; 0% to 100%) as population prevalence changes (x axis; 0% to 100%). The actual prevalence in this study for each of the three causes in panels A to C is indicated with a vertical red line. The vertical blue line in (A) indicates the prevalence for bacterial vaginosis found in the study of Gaydos et al. (Nugent scoring 0 to 3 and 7 to 10 plus modified Amsel's criteria 2/3 without discharge for Nugent scoring 4 to 6; compared to Nugent in this study using 0 to 3 and 7 to 10) (12).