LAUSR

Objectives: Although previous cross-sectional studies have identified correlates of detectable plasma HIV-1 RNA viral load (VL) among HIV-positive people who use drugs (PWUD), longitudinal factors associated with heightened HIV transmission potential have not been well described. Therefore, we longitudinally examined factors associated with amount of person-time spent above log10(1500) copies/ml plasma among HIV-positive PWUD in Vancouver, Canada. Design: Data were derived from a long-running prospective cohort of HIV-positive PWUD linked to comprehensive clinical records including systematic VL monitoring. Methods: We used generalized estimating equations modeling to longitudinally examine factors associated with person-time (in days) with a VL more than log10(1500) copies/ml plasma in the previous 180 days. Results: Between December 2005 and May 2014, 845 PWUD were eligible and included in the study. Participants spent an average of 26.8% of observation time with a VL more than log10(1500) copies/ml. In multivariable analyses, homelessness (Adjusted Rate Ratio [ARR] = 1.45) and lack of social support (ARR = 1.27) were positively associated with person-time with a VL more than log10(1500) copies/ml. Older age (ARR = 0.97) and enrolment in addiction treatment (ARR = 0.75) were negatively associated with the outcome in multivariable analyses (all P < 0.05). Conclusion: Social and structural factors, including periods of homelessness or lacking in social support, were independently associated with greater amount of time with heightened HIV transmission potential. These findings suggest the need for targeted efforts to address modifiable contextual factors that contribute to increased risk of onward HIV transmission among PWUD.