O1-S05.06 Association between prevalentBacterial vaginosis(BV) and HIV Infection among female sex workers at two African and two Indian sites
Authors: Guédou F Aimé , van Damme L , Mirembe F M , Solomon S , Becker M , Deese J , Crucitti T , Taylor D , Alary M 
Published: July 2011

Background

BV is the most common female genital infection, particularly in developing countries and reaches its highest prevalence among female sex workers (FSWs). Over the past decade, evidence has accumulated as to its role in HIV acquisition. If BV actually plays such a role, even a modest relative risk would yield an important attributable risk for HIV, particularly in developing countries where FSWs play a pivotal role in the dynamics of HIV epidemics. Yet, data on this association among FSWs are still scanty. We analysed data from high risk women screened prior to participation in a microbicide trial to estimate BV and HIV respective prevalence and to study their association, in the presence or not of other STIs.

Methods

Data from Kampala, Cotonou, Chennai and Mudhol/Jhamkandi sites were analysed. Socio-demographic, behavioural and medical data were collected through individual interviews. Blood was taken for HIV and syphilis antibody testing. Genital samples were collected for BV diagnosis using Nugent scoring system, of gonorrhoea and chlamydias by SDA and of trichomoniasis (TV) and candidiasis on wet mount. Binomial log regression was used to estimate HIV prevalence ratio (PR) in relation to BV. Fitting of multivariable models was done with backward selection using the approach of proportional change of the PR. Product terms from BV and each of other STIs were included in the final model. Significance level was set at 5% for testing associations and 15% for interactions.

Results

Out of 1491 FSWs, BV data were available for 1367 among whom, BV and HIV prevalences were 47.6% (95% CI=45.0% to 50.3%) and 27.0% (95% CI=24.6% to 29.3%) respectively. In multivariable analysis (Abstract O1-S05.06 table 1), adjusting for site, age, years of education, occupation, current contraceptive method, oral sex, past history of STI, gonorrhoea, candidiasis and syphilis, BV was significantly associated to HIV (adjusted PR=1.20, 95% CI=1.01% to 1.42%, p=0.03). In addition, the PR was negatively modified by TV, whose prevalence was 6.7%: PR was 1.25 (1.05 to 1.48) and 0.76 (0.41 to 1.38) in the absence and the presence of TV respectively (p for interaction =0.12).

Abstract O1-S05.06 Table 1

Final multivariate model *describing association betweenBacterial vaginosisand HIV infection with effect modification by Trichomoniasis, among 1367 FSWs recruited at 2 African and 2 Indian sites

VariablesHIV prevalence by exposure level: ni/Ni(%)Adjusted PR§95% CIp valueBacterial vaginosis: Positive192/651 (29.49)1.251.05 to 1.480.01 Negative177/716 (24.72)1.00––Site: Mudhol/Jhamkandi23/49 (46.94)1.060.71 to 1.580.78 Cotonou123/447 (27.52)0.630.50 to 0.79<0.0001 Chennai56/355 (15.77)0.500.33 to 0.760.001 Kampala (Ref.)167/516 (32.36)1.00––Past history of STI: Yes198/615 (32.20)1.431.21 to 1.70<0.0001 No171/752 (22.74)1.00––Exerting an occupation besides commercial sex work: Yes243/906 (26.82)0.820.65 to 1.030.09 No126/461 (27.33)1.00––Current contraceptive method †: Hormonal65/221 (29.41)0.760.43 to 1.340.34 IUD3/11 (27.27)0.990.35 to 2.820.98 Female sterilisation43/294 (14.63)0.540.31 to 0.940.03 Condom248/809 (30.66)0.890.53 to 1.500.67 None (Ref.)10/31 (32.26)1.00––Oral sex in the past 30 days: Yes5/30 (16.67)0.580.35 to 0.950.03 No364/1337 (27.23)1.00––Age (years): 15–19 (Ref.)10/66 (15.15)1.00–– 20–24100/380 (26.32)1.851.03 to 3.340.04 25–29109/357 (30.53)2.231.24 to 4.000.01 30–3468/221 (30.77)2.701.50 to 4.880.001 35–6082/343 (23.91)2.251.23 to 4.110.01Education duration (years) 0–6240/782 (30.69)1.00–– 7–12124/548 (22.63)0.760.63 to 0.920.005 13–175/37 (13.51)0.500.22 to 1.130.10Gonorrhoea‡: Positive52/111 (46.85)1.521.26 to 1.83<0.0001 Negative316/1253 (25.22)1.00––Candidiasis: Positive118/421 (28.03)1.200.99 to 1.450.06 Negative251/946 (26.53)1.00––Syphilis‡: Positive29/82 (35.37)1.260.96 to 1.670.09 Negative339/1282 (26.44)1.00––Trichomoniasis‡: Positive29/82 (35.37)1.200.82 to 1.740.34 Negative339/1282 (26.44)1.00––BV_TV¶–0.610.32 to 1.130.121.00––

*This model includes, besides the site, all other covariables with p value <0.10 (though removal of neither resulted in a substantial change in the PR estimate during the confounders selection process), as well as TV and the product term between BV and TV.

† = 1 missing value.

‡ = 3 missing values.

§ PR=prevalence ratio.

¶ BV_TV=product term between Bacterial Vaginosis (BV) and Trichomoniasis (TV).

Conclusions

Though its cross-sectional design precludes all directional interpretation of the findings, this study confirms the relationship between BV and HIV among FSWs and warrants prospective studies in this population. The negative modifying effect of TV on this association's measure needs further investigation.