A flexible method to model HIV serodiscordance among couples in Mozambique

Use of "Strengthening Our Vows" Video Intervention to Encourage Negotiated Explicit Sexual Agreements in Zambian Heterosexual HIV Seroconcordant-Negative Couples

Negotiating sexual agreements in combination with couples' voluntary HIV counseling and testing (CVCT) may help further reduce HIV transmission in Zambian concordant HIV-negative couples (CNC). Though CVCT has been shown to reduce HIV transmission in CNC by 47%, approximately half of residual infections occur in this group. We developed a "Strengthening Our Vows" video session to foster communication and negotiation of explicit sexual agreements to reduce concurrent sexual exposures and prevent HIV transmission to the spouse due to unprotected, extramarital sex. CNC were recruited through CVCT services at five clinics in Lusaka and Ndola in 2016. Enrolled CNC attending the facilitated group video sessions were encouraged to discuss sexual agreements at home and return 1-2 weeks later for follow-up assessment. One-fourth of the 580 CNC returning reported a history of extramarital partners and/or a sexually transmitted infection (STI) prior to enrollment. More than 95% reported a friendly, supportive 15-60 min negotiation culminating in an agreement to remain monogamous or disclose sexual contacts and use condoms together until a repeat HIV test 30 days after an outside sexual exposure. Two-thirds of participants identified at least one threat to adherence of their agreements including alcohol use, financial pressures, travel, discord in the home, and post-partum or menstrual abstinence. CNC negotiated explicit sexual agreements to avoid exposure to HIV through concurrent partnerships and protect the spouse in the event of an outside sexual contact. Open communication was a consistent theme to facilitate mutual protective efforts. Long-term follow-up of HIV/STI incidence is ongoing to assess the impact of these agreements.Trial registration This sub-study is part of a trial retrospectively registered on ClinicalTrials.gov (Identifier: NCT02744586) on April 20, 2016.

Factors associated with HIV serodiscordance among couples in Mozambique: Comparison of the 2009 INSIDA and 2015 IMASIDA surveys

Recent studies suggest that a large proportion of new HIV-1 infections in mature epidemics occurs within discordant couples, making discordancy a major contributor to the spread of HIV/AIDS in Africa. This paper aims at assessing changes over a five-year period (2009–2015) on the (risk) factors associated with HIV serodiscordance among couples in Mozambique, using cross-sectional data from the INSIDA and IMASIDA surveys. The pooled data of both surveys were analyzed using a joint model for three parameters characterizing in a particular way disagreement and sero(con/dis)corance between the HIV statuses of couples, as introduced by Aerts et al.: the probability that the female partner is HIV positive, given that both partners differ in their HIV status, the probability that only one partner is HIV positive, given that at least one of the two partners is positive (“positive” serodiscordance), and the probability that both partners are negative given that at most one of the two partners is positive (“negative” seroconcordance). The results reveal similar significant factors and estimates as in Aerts et al. (HIV prevalence, union number for woman, STI for man, condom use by woman and wealth index), but the additional significant factors “condom use by man” (no use had a negative effect on the positive serodiscordance) and “union number for man” (for couples where the man has been married or co-habiting with a woman before had a decreased negative seroconcordance) were identified. The only factor that had a different effect over time (IMASIDA as compared to INSIDA) was the effect of “HIV prevalence of province” on the negative seroconcordance. The negative effect of a higher HIV prevalence was less pronounced in 2015 for negative seroconcordance.

Measures for concordance and discordance with applications in disease control and prevention

Bivariate binary response data appear in many applications. Interest goes most often to a parameterization of the joint probabilities in terms of the marginal success probabilities in combination with a measure for association, most often being the odds ratio. Using, for example, the bivariate Dale model, these parameters can be modelled as function of covariates. But the odds ratio and other measures for association are not always measuring the (joint) characteristic of interest. Agreement, concordance, and synchrony are in general facets of the joint distribution distinct from association, and the odds ratio as in the bivariate Dale model can be replaced by such an alternative measure. Here, we focus on the so-called conditional synchrony measure. But, as indicated by several authors, such a switch of parameter might lead to a parameterization that does not always lead to a permissible joint bivariate distribution. In this contribution, we propose a new parameterization in which the marginal success probabilities are replaced by other conditional probabilities as well. The new parameters, one homogeneity parameter and two synchrony/discordance parameters, guarantee that the joint distribution is always permissible. Moreover, having a very natural interpretation, they are of interest on their own. The applicability and interpretation of the new parameterization is shown for three interesting settings: quantifying HIV serodiscordance among couples in Mozambique, concordance in the infection status of two related viruses, and the diagnostic performance of an index test in the field of major depression disorders.