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Background: Seroadaptive behaviors refer to a wide range of harm reduction practices to decrease HIV transmission risk. Effective implementation of seroadaptive behaviors is dependent on knowledge of one's own serostatus and that of one's sexual partners. Partner-level and environmental-level attributes may affect seroadaptation practices. We assessed factors associated with seroadaptive behaviors., Methods: Men who have sex with men and transgender women were recruited from an HIV pre-exposure prophylaxis clinical trial (iPrEx) with study sites in the US, Peru, Ecuador, Brazil, Thailand, and South Africa. Partnership-level data were collected at the baseline visit for the 3 most recent partners. Participants were considered to have practiced seroadaptive behaviors if: (1) they believed their partner to be HIV-negative, that is, serosorting; or (2) no condomless receptive sex occurred with an HIV-positive or unknown status partner, that is, seropositioning., Results: Of 2331 participants, 41% always practiced seroadaptive behaviors, 36% sometimes did, and 23% never did. Participants enrolled at study sites in the US (P < 0.001) and Peru/Ecuador (P < 0.001) were more likely to practice seroadaptive behaviors, whereas transgender women were less likely to do so (P < 0.001). Seroadaptive behaviors were more likely to occur in relationships with steady partners (P = 0.005) and emotionally close relationships (P = 0.013)., Conclusions: Seroadaptive behaviors were more frequently observed among iPrEx participants from the US, Peru, and Ecuador study sites and among participants in relationships with partners who they were more committed to and felt emotionally close to. Our findings suggest that seroadaptive behaviors may be influenced by social norms that vary geographically and culturally., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Background: As pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate and emtricitabine for the prevention of HIV infection is rolled out internationally, strategies to maintain effectiveness and to minimise adverse effects merit consideration. In this study, we aimed to assess reductions in renal function and predictors of renal toxicity in a large open-label study of PrEP., Methods: As part of the iPrEx open-label extension (OLE) study, men who have sex with men or transgender women aged 18-70 years who were HIV negative and had participated in three previous PrEP trials from Brazil, Ecuador, Peru, South Africa, Thailand, and the USA were enrolled into an open-label PrEP study. There were no restrictions on current renal function for enrolment into iPrEx OLE, in which participants were given combination tablets of tenofovir disoproxil fumarate (300 mg) and emtricitabine (200 mg) and advised to take one tablet per day. At follow-up sessions every 12 weeks, participants' creatinine clearance on PrEP was estimated and in a subset of participants, hair samples were collected to measure tenofovir and emtricitabine concentrations (a measure of adherence and exposure) via liquid-chromatography-tandem-mass-spectrometry. Reductions in creatinine clearance from baseline were calculated and predictors of decline were identified by use of multivariate models. iPrEx is registered with ClinicalTrials.com, number NCT00458393., Findings: Baseline characteristics were similar between all participants in iPrEx-OLE (1224 participants with 7475 person-visits) and those participating in the hair substudy (220 participants with 1114 person-visits). During a median of 72 weeks, the mean decline in creatinine clearance was -2·9% (95% CI -2·4 to -3·4; p trend <0·0001), but declines were greater for those who started PrEP at older ages: participants aged 40-50 years at baseline had declines of -4·2% (95% CI -2·8 to -5·5) and participants older than 50 years at baseline had declines of -4·9% (-3·1 to -6·8). In multivariate models, age and baseline creatinine clearance less than 90 mL/min predicted declines in renal function. We identified a monotonic association between percentage decrease in creatinine clearance and the number of doses of tenofovir disoproxil fumarate and emtricitabine taken per week, as estimated by hair concentrations of tenofovir and emtricitabine (p trend =0·008)., Interpretation: Our data suggest that the frequency of safety monitoring for PrEP might need to be different between age groups and that pharmacological measures can monitor for toxic effects as well as adherence., Funding: National Institutes of Health., (Copyright © 2016 Elsevier Ltd. All rights reserved.)