The Magnetic Couples Study: protocol for a mixed methods prospective cohort study of HIV-serodifferent heterosexual couples' perspectives and use of pre-exposure prophylaxis (PrEP).

Introduction: HIV transmission within serodifferent heterosexual couples plays a key role in sustaining the global HIV pandemic. In the USA, transmission within established mixed-status couples accounts for up to half of all new HIV infections among heterosexuals. Oral HIV pre-exposure prophylaxis (PrEP) is a highly effective prevention method, although underutilised among serodifferent couples. Moreover, there is a dearth of research on US HIV-serodifferent couples' perspectives and use of PrEP, alone or in combination with other prevention methods. In this paper, we describe the study protocol for the Magnetic Couples Study, designed to fill critical knowledge gaps regarding HIV-serodifferent heterosexual couples' perspectives, experiences and utilisation of PrEP.

Methods And Analysis: The Magnetic Couples Study is a mixed methods prospective cohort study designed to describe temporal patterns and identify determinants at multiple levels (individual, couple, HCF) of PrEP outcomes along the care continuum (PrEP awareness, linkage, uptake, retention and medication adherence) among HIV-serodifferent heterosexual couples residing in New York City. The study will also examine clinical management of PrEP, side effects and changes in sexual-related and substance use-related behaviour. A prospective cohort of 230 mixed-status couples already on oral PrEP was recruited, with quarterly assessments over 18 months; in addition, a cross-sectional sample of 150 mixed-status couples not currently on PrEP was recruited. In-depth semistructured qualitative interviews were conducted with a subsample of 25 couples. Actor-partner interdependence modelling using multilevel analysis will be employed for the analysis of longitudinal dyadic data. Framework analysis will be used to analyse qualitative data. A parallel convergent design will be used for mixed methods integration.

Ethics And Dissemination: The study was approved by the University of Rochester Institutional Review Board (RSRB00052766). Study findings will be disseminated to community members and providers and to researchers and policy makers.