O1-S02.02 Are there mutual associations between the incidence of HPV infection and other sexually transmitted infections after controlling for sexual behaviour?
Authors: Soong Thing Rinda , Gravitt P E , Gupta S B , Tadesse A , Kim E , Phongnarisorn C , Wootipoom V , Yuenyao P , Celentano D D 
Published: July 2011

BackgroundWe aimed to determine (i) if other sexually transmitted infections (STIs) increase the risk of incident human papillomavirus (HPV) infection and (ii) if HPV infection predicts the incidence of other STIs.MethodsWomen aged 20–38 years were followed semi-annually for 18 months in Thailand (n=1200). Assessment was made on cervical HPV genotypes, cervical cytology, sexual behaviour, demographic factors and diagnoses of other STIs including chlamydia, gonorrhoea, syphilis, genital herpes and trichomoniasis. Incident detection was defined as any type-specific HPV or other STI which was detected at current visit but not at previous visit. Associations were measured by ORs with 95% CIs estimated in generalised estimating equation models.ResultsDuring follow-up, 241 new cases of HPV, 110 incident cases of high risk (HR)-HPV and 46 new cases of other STIs were observed. Diagnosis of other STIs at previous visit was statistically significantly associated with twofold increased odds of any new HPV detection after controlling for sexual behaviour, age, pap smear status and contraceptive use [adjusted OR (aOR): any HPV: 2.16 (95% CI: 1.08% to 4.34%)] (Abstract O1-S02.02 table 1). No significant association was found between diagnosis of other STIs and subsequent incident detection of HR-HPV [aOR: 2.01 (95% CI: 0.74% to 5.48%)] (Abstract O1-S02.02 table 1). Positive detection of any HPV or HR-HPV predicted nearly twofold increased odds of other STIs with the estimates bordering on statistical significance [aORs: any HPV: 1.81 (95% CI: 0.94% to 3.49%); HR-HPV: 2.00 (95% CI: 0.82% to 4.83%)] (Abstract O1-S02.02 table 2).Abstract O1-S02.02 Table 1Unadjusted and adjusted estimates of detection of other STIs on HPV incidence (total number of visit pairs=3221)Number of visit pairs N=3221Incident detection at current visitUnadjusted OR† (95% CI)Adjusted OR† (95% CI)Diagnosis of the following at previous visitN (col %)New cases of any HPV, n= 241(7.5%) n (row%)New detection of any HPV type across consecutive visitsSTIs other than HPV infection* No3158 (98.0)230 (7.3)1.01.0 Yes63 (2.0)11 (17.5)2.46 (1.31 to 4.62)2.16 (1.08 to 4.34)New cases of any HR-HPV, n=110 (3.4%) n (row%)New detection of any HR- HPV type across consecutive visitsSTIs other than HPV infection* No3158 (98.0)105 (3.3)1.01.0 Yes63 (2.0)5 (7.9)2.42 (0.93 to 6.27)2.01 (0.74 to 5.48)* STIs other than HPV infection included the following: laboratory diagnoses of genital chlamydia, gonorrhoea, syphilis, as well as clinical diagnoses of genital herpes or trichomoniasis.† Estimates adjusted for age and study site at enrolment, as well as the following covariates assessed at each follow-up visit: pap smear diagnosis at previous visit, contraceptive use in last 6 months, number of lifetime partners, partners having sex with others in last 6 months, having new partner in last 12 months, male partner using condom in last 6 months, number of partners in last 6 months.HPV, human papillomavirus; HR-HPV, High-risk HPV, defined as HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 (IARC 2007); STIs, sexually transmitted infections.Abstract O1-S02.02 Table 2Unadjusted and adjusted estimates of HPV detection on incidence of other STIs (total number of visit pairs=3221)Detected with the following at previous visitNew cases of other STIs, n=46 (1.4%) n (row%)New detection of other STIs across consecutive visitsAny HPV No2590 (80.4)31 (1.2)1.01.0 Yes631 (19.6)15 (2.4)1.94 (1.05 to 3.58)1.81 (0.94 to 3.49)New cases of other STIs, n=46 (1.4%) n (row%)New detection of other STIs across consecutive visitsAny HR-HPV No2930 (91.0)38 (1.3)1.01.0 Yes291 (9.0)8 (2.7)2.14 (1.00 to 4.61)2.00 (0.82 to 4.83)Estimates adjusted for age and study site at enrolment, as well as the following covariates assessed at each follow-up visit: pap smear diagnosis at previous visit, contraceptive use in last 6 months, number of lifetime partners, partners having sex with others in last 6 months, having new partner in last 12 months, male partner using condom in last 6 months.Covariates that were found to be statistically significantly associated with the outcomes (p<0.05) and/or significantly influence the effect size of the primary association of interest (≥10%) were included in the final models for confounding control. Parity, smoking status, and other factors measured, such as age of sexual debut and frequency of sex in last 6 months,did notsatisfy these criteria in the data analyses and hence werenotincluded in the final models.HPV, human papillomavirus; HR-HPV, High-risk HPV, defined as HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 (IARC 2007); STIs, sexually transmitted infections.ConclusionsWe show that other STIs increase the risk of HPV incidence after controlling for sexual behaviour. The data qualitatively suggest mutual associations of HPV with other STIs. Further studies are warranted to evaluate if these reflect true biologic interactions between HPV and other sexually transmitted microbial agents, or mere confounding from unmeasured sexual risks.