Background:  There has been considerable controversy regarding the use of HAART among individuals with a history of injection drug use (IDU), as they may be less likely to adhere to HAART, and therefore less likely to experience virologic and immunologic responses. Here, we examine the impact of IDU status and a series of clinical indicators on immunologic response.

Methods:  We assessed outcomes of treatment naïve adults (≥18 years old) initiating HAART after the year 2000. We defined our clinical indicators as: (1) Having <3 versus ≥3 CD4 count measurements in the first year of follow-up; (2) Having <3 versus ≥3 viral load measurements in the first year of follow-up; (3) Having a genotypic resistance testing done at baseline requested by the enrolling physician in samples with viral load >250 copies/mL; (4) Having started therapy with <200 cells/mm³ CD4 cell count; (5) Having started on non-recommended HAART; (6) Having achieved viral suppression at 6 months since therapy initiation. We also adjusted our model for sex, age, CD4 cell count, viral load at baseline, and adherence to therapy during the first 6 months. Immunologic response was defined as the percent change in the 12-month CD4 cell count from the CD4 at baseline. We used partial proportional odds model, given that our response was categorized as percent change ≥100%, percent change >0% and <100% and percent change ≤0%.

Results:  In this study, 402 (N = 1633; 25%) patients reported IDU status. IDU were more likely to be female, younger, have adherence <95% during the first 6 months, <3 CD4 cell count and <3 viral load measurements during the first year on HAART, having started HAART with a CD4 cell count of 160 cells/mm³, and against all odds, being able to achieve suppression at 6 months since the initiation of HAART (P <0.01). The multivariate model estimated that IDU versus non-IDU immunologic responses did not differ significantly when stratified by the clinical indicators. Of note, as seen in the table, IDU and non-IDU had similar overall responses to HAART when stratified by adherence rates. 

Conclusions:  Our results demonstrate that IDU and non-IDU have similar immunologic outcomes on modern HAART. Therefore, it is important that physician-perception be modified regarding the benefits of HAART in the IDU population, in order to reduce premature and avoidable HIV/AIDS morbidity and mortality in this population.