Longitudinal community plasma HIV-1 RNA concentrations

Longitudinal community plasma HIV-1 RNA concentrations and incidence of HIV-1 among injecting drug users: prospective cohort study.

To examine the relation between plasma HIV-1 RNA concentrations in the community and HIV incidence among injecting drug users, Wood and colleagues conducted a prospective cohort study in an inner city community in Vancouver, Canada. Injecting drug users, with and without HIV, were followed up every six months between 1 May 1996 and 30 June 2007. The main outcome measures were estimated community plasma HIV-1 RNA in the six months before each HIV-negative participant’s follow-up visit and associated HIV incidence. Among 622 injecting drug users with HIV, 12 435 measurements of plasma HIV-1 RNA were obtained. Among 1429 injecting drug users without HIV, there were 155 HIV seroconversions, resulting in an incidence density of 2.49 (95% confidence interval 2.09 to 2.88) per 100 person years. In a Cox model that adjusted for unsafe sexual behaviours and using nonsterile syringes, the estimated community plasma HIV-1 RNA concentration remained independently associated with the time to HIV seroconversion (hazard ratio 3.32 (1.82 to 6.08, P<0.001), p="0.175)," style="text-decoration: underline;">a longitudinal measure of community plasma HIV-1 RNA concentration was correlated with the community HIV incidence rate and predicted HIV incidence independent of unsafe sexual behaviours and sharing used syringes. If these findings are confirmed, they could help to inform both HIV prevention and treatment interventions.

This ecological study estimated community plasma viral load from the viral loads of injecting drug users on treatment in this urban community which has a centralised antiretroviral dispensation programme and HIV laboratory. The proportion of patients on 3 or more antiretroviral drugs increased from 8.4% in 1996 to 98.8% in 2007 while both median estimated community plasma HIV-1 RNA concentrations and HIV incidence fell. The likelihood that an HIV-negative injecting drug user had seroconverted since the last clinic visit was correlated with the median estimated community viral load during the prior 6 months. It is not possible to conclude from these data that the association was causal but the fact that the highest rates of HIV seroconversion occurred in the year after the highest community plasma HIV-2 concentration support this hypothesis. These findings no doubt influenced the provincial government to fund an innovative programme to expand access to treatment for street-involved people living in Vancouver’s downtown eastside and downtown Prince George, British Columbia.