Background: In the U.S., the incidence of HIV infection in injecting drug users (IDU) has increased relative to other transmission risk groups over the past 5 years. This has important clinical and public health implications if IDUs have greater barriers to antiretroviral effectiveness than other risk groups. We assessed if there were differences between IDU and non-IDU patients (pts) in the development of AIDS-defining opportunistic illness (OI) other than viral hepatitis from the time the pts started their first HAART.

Methods: We compared IDU (n = 1077) pts with non-IDU (n = 1229) pts who had a CD4 < 350 cells/mm³ when they started HAART. We controlled for financial access, as all pts had access to HAART through insurance or the AIDS Drug Assistance Program. Incidence rates were compared for IDUs and non-IDUs from 1996 through 2002. Cox regression was used to calculate the hazard of OI development over time after starting HAART.

Results: Incidence rates (OIs/100 person-years) are shown for 1996–2002 (through 7/02). Incidence rate ratios (IRR) were calculated for IDU compared to non-IDU.

 

*Adjusted for sex, race, initial CD4, HIV-1 RNA, and regimen (single PI, boosted PI, NNRTI).

 

From 1996–1999, there was a similar decline in OI incidence in IDUs and non-IDUs. However, in 2000 there was a higher IRR in IDUs vs non-IDUs, that increased further in 2001–2002. By Cox regression, the relative hazard (RH) for OI development in IDU vs non-IDU was similar up to 2 years after first HAART use (1 year RH = 0.85; 95%, CI: 0.62, 1.16; 2 year RH = 1.43; 95%, CI: 0.91, 2.21), but was higher in IDU vs non-IDU beyond 2 years of follow-up (RH = 1.88; 95%, CI = 1.15, 3.07). The rate of durable undetectable HIV-1 RNA after 2 years was 31% IDU vs 47% non-IDU (p < 0.01). Change in CD4 from baseline after 2 years was 85/mm3 in IDU and 136/mm³ in non-IDU (p < 0.01).

Conclusions: Even with access to HAART, IDUs are not receiving the same benefit from HAART as non-IDUs. After 2 years, there is a higher risk of failure, and this higher risk appears to be translating into a higher annual rate of OIs in IDUs. These results suggest a higher burden of HIV disease in IDUs with increased opportunity for HIV transmission. This may serve to further expand the HIV epidemic in IDUs.