Diagnosis of Bacterial Vaginosis and evaluation of associated factors: Comparable findings using Hay/ Ison’s and Nugent’s Scoring System

Abstract

Although Nugent’s criterion is considered as the gold standard for the diagnosis of bacterial vaginosis (BV), the method requires an experienced slide reader and considerable time and skill. We compared Hay/ Ison and Amsel with Nugent’s scoring criteria to determine the prevalence and corelates for BV among women of reproductive age attending reproductive health related clinics (family planning, post-natal and sexually transmitted Infection - STI) at Mbagathi County Referral Hospital in Nairobi. Vaginal specimens were collected from 201 consenting women, presenting with or without the vaginal symptoms of vaginitis. BV was diagnosed using Hay/ Ison, Amsel and Nugent’s method while factors corelates were gathered using structured interviews. Sensitivity, specificity, and predictive values for positive and negative test were calculated for both Hay/ Ison and Amsel methods using Nugent criteria as the gold standard. Corelates for BV in this population were evaluated against the three methods. There were 66 cases (32.8%) of BV by Amsel’s method, 79 cases (39.3%) of BV by Hay/ Ison’s Criteria and 72 (35.8%) cases by the Nugent’s method. Using Nugent criteria as the gold standard, the concordant, sensitivity, specificity, positive and negative predictive values of tests were. Amsel: 77.1%, 63.9%, 84.5%, 80.7% and 69.7% respectively, and Hay/ Ison: 96.5%, 100%, 94.6%, 100% and 91.1% respectively. Evaluating the performance of Hay/ Ison test against Amsel criteria, the standard method for clinical diagnosis; offered no improvement in sensitivity 72.7%, specificity 77.1%, NPV 85.3% and PPV 60.8% when compared to Nugent’s score. Factors independently associated with BV infection included. For all the three tests: Presence of clue cells; Nugent and Hay/ Ison methods: education level, marital status and positive for whiff tests: For Nugent and Amsel criteria: Presence of vaginal discharge and for Hay/ Ison test: condom use. Attributes of socio-demographic and sexual hygiene and behavior contributes to high prevalence of BV among women in the capital city of Kenya. The Hay/ Ison’s method shows good agreement with the Nugent criteria and can be recommended as a stand-alone alternative assay to Nugent’s criteria or as a confirmatory test for BV in this population.

Key words: Nugent, Amsel and Hay/ Ison method Bacterial Vaginosis, Test performance, Correlates, Women of Reproductive Age, Western Kenya