Although mortality has decreased significantly and the prognosis for HIV patients has improved since the introduction of highly active antiretroviral therapy (HAART) [1]–[3], the survival of HIV-infected injection drug users (IDUs) may not have improved as much as for persons in other transmission categories. The timeliness of HIV diagnosis and the initiation of HAART are major determinants of survival for HIV-infected people [4]. There is growing evidence that IDUs not only have suboptimal access and adherence to HAART [5], [6] but also tend to begin antiretroviral treatment at a more advanced stage of infection [5], [7]. There are significant public health benefits of early diagnosis and treatment of HIV infection among IDUs. Reports show that IDUs, who know that they are infected with HIV, are more likely to protect their partners from infection reducing further the spread of the virus [8], [9]. An analysis of US population–based data (including IDUs) showed that the survival of IDUs after HIV diagnosis was shorter than that of persons in other transmission categories [10]. Despite earlier research, no findings on late testing and survival data specific to subpopulations of HIV-infected IDUs have been published. We wished to determine whether demographic factors such as race/ethnicity, sex, and age affect prognosis in the HAART era. Therefore, using data from the national HIV/AIDS surveillance system of the Centers for Disease Control and Prevention (CDC), we examined the proportions of subpopulations of IDUs who received a late HIV diagnosis and the determinants of disease progression and survival. Understanding the problem of late HIV diagnosis and determinants of survival for IDUs is important to the development and implementation of HIV prevention efforts.

In 1994, CDC implemented a uniform system for national surveillance of HIV infection integrated with AIDS surveillance, and 25 states with confidential name-based HIV infection reporting started submitting case reports to the CDC. Over time, additional areas implemented confidential name-based HIV infection reporting and started submitting data to CDC. For our analyses, data were available from 33 states (Alabama, Alaska, Arizona, Arkansas, Colorado, Florida, Idaho, Indiana, Iowa, Kansas, Louisiana, Michigan, Minnesota, Mississippi, Missouri, Nebraska, Nevada, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, West Virginia, Wisconsin, and Wyoming). We analyzed cases in adults and adolescents, aged 13 years and older, for whom HIV diagnosis was made during 1996–2004 and who were reported to CDC through June 2007 from the 33 states. Persons with HIV infection were defined as those who had received a diagnosis of HIV with or without a diagnosis of AIDS at the time of HIV diagnosis. HIV diagnosis was considered late if an AIDS diagnosis was made <12 months after the HIV diagnosis [11]. HIV diagnosis was considered concurrent when AIDS diagnosis was made at or within the same calendar month of HIV diagnosis. AIDS is defined by a CD4⁺ T-cell count <200 cells/µL or by an AIDS-defining illness.

Despite the well-known benefits of early detection and the availability of treatment for HIV infection, 42.2% of HIV-infected IDUs received a diagnosis of AIDS within 12 months after receiving a diagnosis of HIV infection. IDUs whose diagnosis is made late in the course of HIV infection may unknowingly transmit infection and once diagnosed may have worse outcomes. In our analysis we found that survival among IDUs was shorter than among other HIV risk groups. The proportion of IDUs who did not progress to AIDS 3 years after HIV infection was lower among men. IDUs with a diagnosis of HIV at older ages or with more severe disease (lower CD4⁺ T-cell count at AIDS diagnosis) had shorter survival.

Our results were consistent with earlier findings of shorter survival after HIV diagnosis among IDUs compared with persons in other transmission categories [10]. Disparities between risk groups in the receipt of, or the adherence to, treatment might explain the observed differences in survival. Numerous studies have documented that the prescription of, and the adherence to, HAART is lower among IDUs than among persons who do not use drugs [14]–[16] because of IDUs' disadvantaged social situation, financial difficulties, and lack of family and social support [17]–[19]. Even in settings that provide free HIV treatment, low rates of utilization among eligible IDUs have been reported [20]. The use of HAART has been shown to be less common among active IDUs who do not have symptomatic diseases and thus have less contact with health care providers [5]. The strategies that have improved access and adherence to antiretroviral medications among HIV-infected IDUs include directly observed therapy, access to medical services without appointment, on-site pharmacists (at medical clinics), and improved access to addiction treatment [15], [21]. Information on treatment and type of health insurance, which might be related to receipt of treatment, was not available. In addition, deaths due to other causes (end-stage liver disease, bacterial infections), which are more common among IDUs than other risk groups, may play a role in the shorter survival of IDUs [22]. Future studies should assess whether the receipt of, or the adherence to, treatment can explain poorer survival of IDUs.

Shorter survival among IDUs may also be linked to late testing. A large proportion of IDUs learned of their HIV infection late in the course of disease, reducing optimal benefit from new therapeutic strategies, which remains a major public health issue. In an HIV testing study of persons at high risk for HIV infection, researchers found that the main reasons for not being tested were denial of HIV risk factors and fear of being HIV-positive [23]. Efforts to test HIV-infected people as early as possible should be made by increasing the awareness of HIV risk factors and decreasing the number of missed opportunities for testing. Addiction treatments and needle exchange programs are important venues to offer testing for HIV-positive IDUs. Understanding the psychological and social reasons for late testing among IDUs could help public health officials develop initiatives to reduce barriers to testing. CDC recommends routine testing in medical settings of all persons aged 13–64 years [24] to reduce the number of persons unaware of their HIV infection and diagnose HIV infection earlier in the disease process.

Similar to earlier analyses [11], our analysis revealed a lower probability of progression from HIV infection to AIDS within 1 year and within 3 years for female IDUs, compared with male IDUs. This finding may be explained by prenatal tests and gynecologic follow-up, which could increase the likelihood of HIV testing among female IDUs [25]. Persons, including IDUs, who receive a diagnosis of HIV infection at an older age are at increased risk of progressing from HIV diagnosis to AIDS or death within 1 and 3 years. Older age is a strong risk factor for disease progression because older persons have diminished immune function and more comorbidities [10], [26], [27]. In addition, our results show that older IDUs were more likely to receive a late diagnosis. As expected, CD4⁺ T-cell count at AIDS diagnosis was a strong determinant of survival [13], [28]. Guidelines for the use of antiretroviral medications in adults and adolescents infected with HIV type 1 recommend initiating treatment in patients with a history of an AIDS-defining illness or with a CD4⁺ T-cell count of <350 cells/µL [29]. Kohli et al. [22] reported that HIV-infected IDUs who began taking HAART at a CD4⁺ T-cell count of >200 cells/µL survived longer than those who began taking HAART at a CD4⁺ T-cell count of ≤200 cells/µL. Unfortunately, a substantial proportion of IDUs in the United States received a concurrent diagnosis of HIV and AIDS, and 38.2% of these persons had very low CD4⁺T-cell counts at HIV diagnosis (<50 cells/µL).

Our analyses are subject to several limitations. Although our data represent the largest set of available population-based data on HIV-infected persons, the data from 33 states may not be nationally representative, and it is not known whether the results can be extrapolated to the United States as a whole. However, all states and the District of Columbia have now implemented confidential name-based HIV reporting. The increased number of name-based reporting states will allow a more accurate description of the size of the population of HIV-infected IDUs and the determinants of disease severity. Risk factor information was missing for 27.1% of the persons with a diagnosis of HIV infection, so the data could not be included in our analysis. We also found that a large proportion of HIV-infected persons did not have a reported CD4⁺ T-cell count, which may reflect a lack of access to care or differences in reporting (e.g., state laws requiring laboratories to report). Finally, special research should be undertaken to better understand the reasons for late HIV testing (routine surveillance does not collect information about the reasons for late HIV testing).

In summary, we found that for large proportions of HIV-infected IDUs, diagnosis was made late in the disease process and HIV infection progressed to AIDS within 3 years. Also, survival among IDUs was shorter than among other HIV risk groups. These findings suggest that public health and medical services need to be improved to better target interventions for prolonging the lifespan of IDUs living with HIV infection, in addition to primary HIV prevention initiatives.