WEAC0202 - Oral Abstract Session
Association of injectable contraception and risk of HIV-1 acquisition in women in HIV-1 serodiscordant partnerships: persistence of effect in multiple sensitivity analyses
Presented by Renee Heffron (United States).
R. Heffron1, D. Donnell2, H. Rees3, C. Celum1, N. Mugo1,4, E. Were5, G. de Bruyn3, E. Nakku-Joloba6, K. Ngure4, J. Kiarie1,4, R. Coombs1, J. Baeten1, Partners in Prevention HSV/HIV Transmission Study Team
1University of Washington, Seattle, United States, 2Fred Hutchinson Cancer Research Center, Seattle, United States, 3University of Witswatersrand, Johannesburg, South Africa, 4Kenyatta National Hospital, Nairobi, Kenya, 5Moi University, Eldoret, Kenya, 6Makerere College of Health Sciences, Kampala, Uganda
Background: We recently
reported that women in HIV-1 serodiscordant partnerships using injectable
contraceptives had a 2-fold increase in HIV-1 acquisition risk (aHR=2.05,
p=0.04; Heffron et al., Lancet Infectious Diseases 2012). Here, we report the results from multiple additional
sensitivity analyses examining the robustness of our findings.
Methods: We used Cox proportional hazards regression, adjusting for age, male
partner's plasma viral load, and time-dependent unprotected sex and pregnancy,
to compare HIV-1 incidence in women using injectable contraception to women
reporting no hormonal method.
Sensitivity analyses included: 1) additional or alternative covariates
to adjust for sexual behavior, 2) restricting to follow-up periods when
unprotected sex was reported, 3) censoring visits after a woman switched her
contraceptive method (to minimize the effect of changing methods on risk), and 4)
restricting to consistent injectable users outside of South Africa (with access
to only injectable depot medroxyprogesterone acetate [DMPA]).
Results: In all models, the approximately 2-fold increase in HIV-1 acquisition risk
persisted. Neither additional adjustment
for coital frequency (aHR=2.06, p=0.04) nor adjustment for the male partner's
report of unprotected sex (where accuracy is less likely influenced by the
woman's contraceptive choice, aHR=2.03, p=0.07) influenced the results. When limited to periods when unprotected sex
was reported or including only visits prior to the first contraceptive switch,
the aHR were 2.29 (p=0.17) and 2.62 (p=0.07), respectively. Finally, when only consistent, presumed DMPA
users were retained (i.e. South Africans excluded), injectable contraception
was associated with a nearly 4-fold increased HIV-1 risk (aHR=3.93,
Conclusions: Injectable contraception continued to be associated with increased HIV-1
risk despite numerous methods to control for potential imprecision in contraceptive
exposure measurement and/or key behavioral confounders. Some analyses had p-values >0.05 due to
reduced statistical power but the magnitude of association continued to be as
strong as that seen in our primary analytic model.
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