Since its introduction in the mid-1990s, the benefits of antiretroviral therapy for the management of HIV disease have been well established [1,2]. New antiretroviral regimens have proved to be effective in decreasing HIV plasma viral load, improving CD4 cell counts, and have substantially altered the natural history of HIV infection [3,4]. As a result, substantial improvements in HIV-related morbidity and mortality have been documented among persons receiving appropriate antiretroviral regimens, and in many areas of the world, HIV infection is increasingly being viewed as a chronic and manageable illness [5,6].
Nevertheless, the clinical management of HIV disease continues to present major challenges. Treatment of HIV disease with the regimens that are presently available aims to prevent progression to AIDS or death by reducing plasma HIV RNA to as low a level as possible for as long as possible [7,8]. The eradication of HIV from the individual is not considered possible with presently available therapeutic agents. As such, persons undergoing treatment for HIV disease must take a daily regimen of at least three antiretroviral drugs (i.e., highly active antiretroviral therapy, or HAART), and follow a scheduled dosing protocol that often involves coordination of dietary intake . To date, a great deal of effort has been expended in evaluating patient, physician, and healthcare delivery-related factors that may limit or enhance daily adherence to antiretroviral therapy [10–15].
A related challenge, which is the focus of this review, involves the lesser-studied problem of access to antiretroviral therapy. While issues surrounding access to antiretroviral therapy are most pressing in the developing world, where HIV treatment remains prohibitively expensive , emerging data suggest that high levels of ongoing HIV/AIDS mortality persist in the developed world, in a large part due to limited use of HAART . Although a proportion of these deaths are probably due to sub-optimal adherence to daily antiretroviral therapy and inability to tolerate the side effects of HAART , there is growing evidence that a high proportion of the ongoing AIDS mortality in the developed world is due to poor access to therapy among disadvantaged or marginalized populations.
Limited access to HAART may be of particular concern for specific populations, and may involve treatment discontinuation and/or intermittent use of antiretrovirals, as well as premature mortality among those who never accessed HIV treatment prior to AIDS diagnosis or death. There is evidence that both of these concerns are common in developed world settings, even in countries where HIV/AIDS patients are eligible for antiretroviral therapy and medical care free of charge [19,20]. The following review will outline the evidence that suggests that limited retention in treatment and poor access to antiretroviral therapy are contributing to ongoing AIDS mortality in developed world settings. In addition, we will review the research to date on barriers to access and retention in HIV treatment, as well as strategies that may improve access to antiretrovirals among at-risk populations.
Populations at risk of poor access to HAART
There is growing evidence that emerging disparities in HIV-related mortality are due to problems with access to antiretrovirals and retention in treatment among specific sub-populations. These populations include groups that have traditionally been at risk of inferior access to health care such as persons of lower socio-economic status, ethnic minorities, and injection drug users (IDU) [21–23]. Limited access may stem from issues ranging from physician reluctance to prescribe HAART based on presumed inability to adhere to therapy, to cultural barriers that may result in individuals refusing HAART when it is offered. As will be discussed below, among persons with HIV infection, female gender has also been consistently associated with poorer access to antiretroviral therapy.
The role of socio-economic status in HIV disease progression has been the focus of much study since it was first found to be an independent predictor of HIV disease progression prior to the advent of HAART [24,25]. This finding was consistent with what has been observed for many other diseases , and subsequent studies suggested that differences may be due to poor access to HIV/AIDS care among lower income patients [27,28]. A recent Canadian study has demonstrated substantially elevated mortality after the initiation of antiretroviral therapy among lower income HIV- infected patients, due to the more common use of sub-optimal dual therapy in lower income individuals . In this study, the prescription of sub-optimal dual therapy persisted after adjustment for baseline clinical characteristics including plasma HIV RNA and CD4 cell count. Since provision of antiretroviral therapy is free in this setting, prescription of dual therapy to lower income individuals must be attributed to non-financial concerns, such as physician unwillingness to prescribe protease inhibitors to patients perceived to be non-adherent. Other studies have similarly demonstrated that persons of lower socio-economic status are less likely to be prescribed antiretroviral therapies [30,31], and these implications have been well described .
Ethnic minorities and females have also been shown to have poorer access to antiretroviral therapy. These concerns were first reported prior to the advent of HAART. In one US study, it was demonstrated that AIDS mortality and opportunistic infections were elevated among African American patients, and that the differences were attributable to more advanced HIV disease at presentation for zidovudine therapy and less frequent use of PCP prophylaxis among this population . A subsequent study, demonstrated that African Americans were significantly less likely to have been prescribed antiretroviral therapy or PCP prophylaxis at the time of being referred to an HIV clinic . With regard to gender, another US study demonstrated that 58% of women delayed entry into specialized HIV care for ≥ 3 months following an HIV diagnosis, and that upon entry 65% were symptomatic and 40% were severely immunocompromised .
These ethnic and gender disparities have persisted since the introduction and widespread use of HAART. For instance, a large representative sample of HIV-infected adults from across the US demonstrated that, while problems with access to HIV care have diminished over time, as late as 1998 fewer African Americans and women had started taking antiretroviral medication after adjustment for CD4 cell count . Similarly, another sample of that cohort looked carefully at inhibitors and facilitators of access and found that women, African Americans, and the least educated were less likely to access HAART . These findings are consistent with the results from studies evaluating access at the state and city level [36–38].
Although social and cultural factors may explain some of the association between socio-economic status, race, gender, and poor access to therapy, there is little doubt that much of the association is due to the fact that in comparison with HIV-infected individuals with higher access to therapy, in particular gay and bisexual males , HIV-infected illicit drug users may be more likely to be women, ethnic minorities, and have lower incomes. In addition, those infected through sexual contact with IDU and/or through the sex-trade may be more likely to reside in lower income areas, to be female, and to be ethnic minorities.
Numerous studies have shown illicit drug use to be a major barrier to accessing antiretroviral therapy . For instance, a Swiss study demonstrated that active injection drug users outside a drug treatment program, and those who acquired HIV infection through injection drug use had a significantly higher risk of inadequate treatment . An Italian study that stratified patients by HIV exposure category found that IDU began pre-AIDS antiretroviral therapy significantly later than homosexual men and heterosexuals, and that the risk of disease progression was elevated among IDU within a cohort primarily using zidovudine . A subsequent Italian study found that patients with a history of injection drug use were significantly less likely to be prescribed protease inhibitors among a population eligible for antiretroviral therapy . Similarly, a French study demonstrated that despite regular access to AIDS specialized hospital care, continued drug use was a major barrier to being prescribed antiretroviral treatment . Similar findings have been reported from the US where it has been found that HIV-infected IDU who were not receiving antiretrovirals have tended to be active drug users [37,44]. Among injection drug users in Canada, younger age and female gender has been associated with being less likely to have ever received any antiretroviral therapy after adjustment for HIV RNA and CD4 cell count . Interestingly, in comparing access to antiretroviral therapy among medically eligible IDUs in Vancouver and Baltimore between 1996 and 1998, similar proportions had not received any therapy (49 versus 40%, respectively), but IDUs in Vancouver were less likely to receive monotherapy (6 versus 14%, respectively) [44,45].
A final population that may be at risk of poor access and outcomes on HAART are those that are reluctant to seek HIV testing, and hence initiate antiretroviral therapy at a very late stage of HIV infection when the effectiveness of HAART may be compromised and opportunistic infections may preclude the use of antiretroviral therapy. This concern has been demonstrated in various settings in Europe  and North America . The scale of this concern is highlighted by an international collaboration of 13 observational HIV treatment databases which demonstrated that of the 12 574 patients included in the study 5224 (41.5%) initiated HAART with a CD4 cell count < 200 × 106 cells/l . Previous studies have demonstrated that some populations, particularly injection drug users, ethnic minorities (both African Americans and Hispanics, and recent immigrants in from developing countries), and persons infected through heterosexual contact may initiate therapy at lower CD4 cell counts [31,48–51].
Access to and discontinuation of HIV treatment
As most studies have been conducted among cohorts still living with HIV, it is presently not known to what extent apparent disparities in access to antiretrovirals will improve as HIV-disease becomes more advanced among those with lower access . For instance, there is evidence that differences in access between populations may diminish to some extent over time,  and that some populations, particularly injection drug users, may initiate therapy at lower CD4 cell counts [31, 48,49].
Nevertheless, there is emerging evidence to suggest that these disparities often persist until AIDS and/or death. For example, although the numbers of AIDS deaths and AIDS diagnoses decreased dramatically in the US with the advent of HAART, the proportional decreases in mortality were smallest among African Americans . These findings are not unique to the United States. For instance, in the province of British Columbia, Canada, where HIV antiretroviral therapy is available free of charge, of the 1239 deaths that were attributed to HIV-infection during the period 1995 to 2001 406 (32.8%) occurred amongst persons who never accessed any HIV treatment . Preliminary analysis of these data suggest that both females and ethnic minorities are more likely to die without ever receiving antiretroviral treatment .
In addition to complete lack of access to antiretroviral therapy prior to death, treatment discontinuation and ‘intermittent’ use of antiretrovirals have also become a growing concern. Studies have commonly identified both side effects of antiretroviral therapy and history of injection drug use to be associated with therapy discontinuation [53–55]. An acknowledged limitation of these studies stems from the fact that they are commonly based on selected samples of patients who return to clinics and/or fill out surveys, and population-level estimates of treatment discontinuation are less commonly available. However, evidence of the high prevalence and negative impact of poor retention in treatment comes from population-based studies that have sought to derive population-level estimates of patient adherence by using prescription refill compliance as a surrogate. Several recent studies have applied this approach to estimate the impact of exposure to therapy on disease progression, and have demonstrated that ‘adherence,’ defined based on prescription refills, is strongly and independently associated with survival [56,57]. For instance, among the 1422 treatment naïve patients who initiated HAART in British Columbia, Canada since July 1996, 355 (25%) picked up medications < 75% of the time during their first year on therapy. Among those who picked up antiretrovirals < 75% of the time, there was nearly a three-fold increased risk of death compared to those who picked up antiretrovirals at least 75% of the time. Although further evaluation of these data are necessary, among the 193 (13.6%) deaths observed among this cohort of patients as of 31 March 2002, 27 (14%) were among individuals who discontinued therapy within 1 month of initially starting HAART and did not re-initiate therapy again prior to death (BC Centre for Excellence in HIV/AIDS unpublished data).
Barriers to the use of antiretroviral therapy
The provision of healthcare services to marginalized populations has historically been compromised by an array of complex social dynamics. This is particularly the case for those addicted to drugs and alcohol, the mentally ill, and the homeless . Among the greatest challenges for the increasing population infected with HIV through injection drug use stems from the fact that, in most countries around the world, the most commonly applied approach to reducing drug use-related problems is to impose criminal sanctions on those who use illicit drugs. This is demonstrated by a recent report which estimated that 20 to 26% of all people living with HIV in the United States in 1997 passed through a correctional facility that year . As a result of enforcement efforts in the community, those addicted to illicit drugs are often driven physically and socially into environments where they are extremely difficult to reach for the purpose of providing medical services [60–63]. Among patients who are incarcerated, transition between prison and the community is often associated with interruptions in care and treatment.
In addition, a commonly reported barrier to accessing antiretrovirals may be physicians who are skeptical about injection drug users’ ability to adhere to therapy, and it is likely that concerns regarding possible transmission of antiretroviral resistant virus has influenced prescribing decisions . This is supported by previous surveys of physicians showing that physician's judgment of patient adherence is critical for the prescription of HAART [40,43]. Physicians have noted that patient homelessness, heavy alcohol use, injection drug use, and prior psychiatric hospitalization have all contributed to their reluctance to initiate HAART .
These findings raise concerns for several reasons. First, a recent study demonstrated that a substantial proportion of homeless and marginally housed individuals managed high adherence to antiretroviral therapy including protease inhibitors (PIs), and that resistance to PIs were rare among those that were non-adherent . Furthermore, ethical analyses have suggested that physicians should not indefinitely withhold HAART from patients who are presumed to be poorly adherent [58,67,68]. This argument is strengthened by the studies that have consistently demonstrated that providers may be poor judges of patient adherence [69–71].
Other service delivery barriers to accessing antiretroviral therapy may range from geographic to cultural barriers. For instance, an earlier review suggested that geographic location may influence access to HAART, with more accessible locations possibly being associated with better access . This is consistent with other studies that have found missing clinic visits to be a strong predictor of virological failure . Finally, the consistent associations between ethnic minority status and poor access suggest that cultural differences, as a result of language differences, perceived or real stigma, or other social barriers contribute to limited access [30,33,36–38].
Finally, even when physicians are willing to prescribe antiretroviral therapy and no other barriers are in place, illicit drug use, mental illness, and homelessness may all present major barriers to accessing and retention in an HIV treatment program [37,44,58,73]. While each of these issues presents unique challenges, there are promising strategies that may help to address these concerns.
Strategies for improving access and retention
Whereas interventions to improve daily adherence to antiretroviral therapy have received a growing amount of attention [74–76], limited data exist with regard to strategies that may optimize access and retention in HIV treatment among populations that have traditionally had poor access to antiretroviral therapy. Nevertheless, through what is known about the significant barriers that presently exist, and what has been learned from experience with other chronic diseases, several strategies deserve further consideration.
Among the best sources of evidence for strategies that may improve access and retention in HIV/AIDS treatment arise from interventions that have successfully delivered healthcare to other marginalized populations. Among adherence interventions, the highest rates of treatment retention and adherence to therapies have been observed with patients enrolled in directly observed therapy (DOT) programs for the treatment of tuberculosis [77,78]. In one DOT study, 77% of IDU took 100% of prescribed isoniazid therapy to prevent tuberculosis, a markedly higher adherence rate in comparison to those randomized to self-administered therapy regardless of counseling and education, although both groups were successfully retained in the study up to 6 months .
However, doubts have been raised about the feasibility of directly observed therapy for HIV infection for several reasons, not the least of which is that it may require many years of supervised therapy. In addition, challenges presented by extending directly observed therapy to the treatment of HIV include the potentially negative impact on individual freedoms, as well as concerns that patients may be reluctant to disclose toxicities and side effects out of fear of interrupting scheduled reimbursement [79,80]. Furthermore, among the few studies of directly observed therapy for HIV infection that have been reported [81,82], it has been noted that it is difficult to determine what effect direct supervision or other aspects of assisted adherence programs have had the largest effect . Nevertheless, the ability to retain patients in treatment and ensure high adherence suggests that the directly observed therapy model deserves further consideration.
With regard to physician–patient relationships, whereas physician reluctance to prescribe antiretrovirals has been shown to be a barrier to access, it is important to note that certain physician-related characteristics have also been strongly associated with better access, adherence, and retention in treatment. For instance, satisfaction with one's physician has been associated with higher levels of adherence , and willingness to initiate HAART has been associated with patient trust in their physician . In addition, among injection drug users, being treated by a physician with greater experience treating HIV disease was associated with accessing antiretroviral therapy [45,84]. These findings demonstrate both that the physician–patient relationship is critical , and that care for populations at risk of poor access is best delivered by highly experienced physicians, especially considering that patients at risk of poor access may face additional challenges such as HCV co-infection, mental illness, and addiction.
In addition, studies have consistently shown that the provision of drug treatment services can enhance adherence and retention in HIV treatment for illicit drug users. Among the most well-evaluated strategies has been the provision of methadone maintenance therapy (MMT) with antiretroviral therapy, which has been demonstrated to improve outcomes from HAART among HIV-infected IDU [86,87]. As such, efforts should be made to remove barriers to the use of MMT among opiate-dependent, HIV-infected patients who are willing to initiate substitution therapy with MMT . However, there is sufficient evidence to demonstrate that wider access to methadone alone will not be sufficient to close that gap for many opiate-dependent patients. First, many studies of patients successfully treated with antiretrovirals and MMT are often based on selected clinic-based samples, and both observational and randomized studies have demonstrated the high rates of loss to follow-up among patients initiating MMT [89,90]. Although still controversial in many settings, heroin prescription programs appear to have substantial potential to improve retention and treatment outcomes among intractable opiate addicts [91,92]. The randomized trial that has been proposed to take place in three Canadian cities does not exclude HIV-infected opiate addicts, and it will be interesting to see if differences emerge between the control arm (MMT) and prescribed heroin with regard to antiretroviral access and retention in HIV treatment .
The growing number of HIV-infected individuals who are using methamphetamine or cocaine may be even more difficult to reach with health care services, and present even greater challenges with regards to the delivery of HAART . These challenges stem from the effects of the drugs themselves, which often lead to chaotic behavior, as well as the higher frequency of injections and lack of pharmacologic replacement as in the case of heroin/methadone . For these individuals, efforts should be made by the physician to help stabilize them when possible [58,85], and there is also evidence that meeting users on their own turf has substantial potential. For instance, a novel project initiated in San Francisco runs out of a storefront office in the heart of a high HIV prevalence inner-city neighborhood . The program offers both medical and social services, several of which have been shown to improve access to antiretrovirals, including HIV specialist nurses, access to medical services without appointment, and an onsite pharmacist [30,44,97]. Interestingly, the project also offers harm reduction services including needle exchange, which may help to attract eligible patients into their other programs including drug treatment and medical care . Among HIV-infected individuals retained in the program, 64% achieved HIV RNA < 500 ×106 cells/l, and only two patients had shown an increase in HIV RNA relative to their pre-program levels . Programs that seek to improve access to healthcare by reducing socio-cultural and geographic barriers are an important area for further study .
We now have a great deal of evidence demonstrating that lower income populations, women, ethnic minorities, and illicit drug users are at risk of poor access to antiretroviral therapy and higher rates of treatment discontinuation. Although the majority of these studies have been conducted among living cohorts, data is emerging to suggest that limited access is contributing to the ongoing HIV/AIDS mortality rates in the developed world.
Fears regarding the potential for community-wide transmission of antiretroviral resistant HIV among the homeless, mentally ill, and injection drug users have thus far largely been unfounded [58,64, 66,100]. Although this concern deserves continued monitoring, in many instances it is likely that resistance is not observed because a proportion of these patients will cease antiretroviral therapy outright or will be insufficiently adherent for resistance to develop .
The above issues have several implications. First, interventions to improve retention among those who initiate therapy are urgently required, and efforts are needed to ameliorate barriers to treatment retention and adherence. Second, among individuals who have not accessed therapy, strategies to improve contact with HIV care providers are needed. When contact is made, guidelines for physicians must be based on available evidence [69–71]. This evidence suggests that physicians should seek to address modifiable barriers to adherence and retention in HIV treatment prior to the start of therapy among patients not requiring immediate treatment [58,68]. In addition, no patient should be denied the opportunity to initiate HAART regardless of perceived or real barriers to optimal adherence including continued illicit drug use. Given that the extent of the HIV/AIDS public health crisis, and since the full benefits of HAART are not compromised when patients are successfully retained in treatment, regardless of ethnicity, gender, and history of injection drug use [55,101], efforts to address social, cultural, and medical barriers are an urgent priority.
The authors wish to express their gratitude to Dr Samuel Bozzette, Director, Health Services Research, VA San Diego for his thoughtful suggestions on an earlier draft of this manuscript. E.W. is supported by the Michael Smith Foundation for Health Research.
1. Palella FJ, Jr., Delaney KM, Moorman AC, Loveless MO, Fuhrer J, Satten GA, et al
. Declining morbidity and mortality among patients with advanced human immunodeficiency virus infection. HIV Outpatient Study Investigators [see comments].N Engl J Med
2. Hogg RS, Heath KV, Yip B, Craib KJ, O'Shaughnessy MV, Schechter MT, et al
. Improved survival among HIV-infected individuals following initiation of antiretroviral therapy.JAMA
3. Wood E, Yip B, Hogg RS, Sherlock CH, Jahnke N, Harrigan RP, et al
. Full suppression of viral load is needed to achieve an optimal CD4 cell count response among patients on triple drug antiretroviral therapy.AIDS
4. Moore RD, Chaisson RE: Natural history of HIV infection in the era of combination antiretroviral therapy.AIDS
5. Ledergerber B, Egger M, Opravil M, Telenti A, Hirschel B, Battegay M, et al
. Clinical progression and virological failure on highly active antiretroviral therapy in HIV-1 patients: a prospective cohort study. Swiss HIV Cohort Study.Lancet
6. Hogg RS, Yip B, Chan KJ, Wood E, Craib KJ, O'Shaughnessy MV, et al
. Rates of disease progression by baseline CD4 cell count and viral load after initiating triple-drug therapy.JAMA
7. Yeni PG, Hammer SM, Carpenter CC, Cooper DA, Fischl MA, Gatell JM, et al
. Antiretroviral treatment for adult HIV infection in 2002: updated recommendations of the International AIDS Society-USA Panel.JAMA
8. Chun TW, Fauci AS. Latent reservoirs of HIV: obstacles to the eradication of virus.Proc Natl Acad Sci U S A
9. Ickovics JR, Meade CS. Adherence to HAART among patients with HIV: breakthroughs and barriers.AIDS Care
10. Bangsberg DR, Bronstone A, Hofmann R. A computer-based assessment detects regimen misunderstandings and nonadherence for patients on HIV antiretroviral therapy.AIDS Care
11. Catz SL, Kelly JA, Bogart LM, Benotsch EG, McAuliffe TL. Patterns, correlates, and barriers to medication adherence among persons prescribed new treatments for HIV disease.Health Psychol
12. Chesney MA, Ickovics JR, Chambers DB, Gifford AL, Neidig J, Zwickl B, et al
. Self-reported adherence to antiretroviral medications among participants in HIV clinical trials: the AACTG adherence instruments. Patient Care Committee & Adherence Working Group of the Outcomes Committee of the Adult AIDS Clinical Trials Group (AACTG).AIDS Care
13. Gifford AL, Bormann JE, Shively MJ, Wright BC, Richman DD, Bozzette SA. Predictors of self-reported adherence and plasma HIV concentrations in patients on multidrug antiretroviral regimens.J Acquir Immune Defic Syndr
14. Roberts KJ. Physician-patient relationships, patient satisfaction, and antiretroviral medication Adherence among HIV-infected adults attending a public health clinic.AIDS Patient Care STDS
15. Murphy DA, Roberts KJ, Martin DJ, Marelich W, Hoffman D. Barriers to antiretroviral adherence among HIV-infected adults.AIDS Patient Care STDS
16. Wood E, Braitstein P, Montaner JS, Schechter MT, Tyndall MW, O'Shaughnessy MV, et al
. Extent to which low-level use of antiretroviral treatment could curb the AIDS epidemic in sub-Saharan Africa [see comments].Lancet
17. Wood E, Schechter MT, Tyndall MW, Montaner JS, O'Shaughnessy MV, Hogg RS. Antiretroviral medication use among injection drug users: two potential futures.AIDS
18. Paterson DL, Swindells S, Mohr J, Brester M, Vergis EN, Squier C, et al
. Adherence to protease inhibitor therapy and outcomes in patients with HIV infection.Ann Intern Med
19. Wood E, Montaner J, Yip B, Schechter M, O'Shaughnessy MV, Hogg R. Prevalence and correlates of untreated HIV-1 infection among persons who have died in the era of modern antiretroviral therapy.J Infect Dis
20. Karon JM, Fleming PL, Steketee RW, De Cock KM. HIV in the United States at the turn of the century: an epidemic in transition.Am J Public Health
21. Fein O. The influence of social class on health status: American and British research on health inequalities.J Gen Intern Med
22. Montgomery LE, Kiely JL, Pappas G. The effects of poverty, race, and family structure on US children's health: data from the NHIS, 1978 through 1980 and 1989 through 1991.Am J Public Health
23. Pappas G, Queen S, Hadden W, Fisher G. The increasing disparity in mortality between socioeconomic groups in the United States, 1960 and 1986.N Engl J Med
24. Schechter MT, Hogg RS, Aylward B, Craib KJ, Le TN, Montaner JS. Higher socioeconomic status is associated with slower progression of HIV infection independent of access to health care.J Clin Epidemiol
25. Hogg RS, Strathdee SA, Craib KJ, O'Shaughnessy MV, Montaner JS, Schechter MT. Lower socioeconomic status and shorter survival following HIV infection [see comments].Lancet
26. Wood E, Sallar AM, Schechter MT, Hogg RS. Social inequalities in male mortality amenable to medical intervention in British Columbia.Soc Sci Med
27. Chaisson RE, Keruly JC, Moore RD. Race, sex, drug use, and progression of human immunodeficiency virus disease.N Engl J Med
28. Easterbrook PJ, Keruly JC, Creagh-Kirk T, Richman DD, Chaisson RE, Moore RD. Racial and ethnic differences in outcome in zidovudine-treated patients with advanced HIV disease. Zidovudine Epidemiology Study Group.JAMA
29. Wood E, Montaner JS, Chan K, Tyndall MW, Schechter MT, Bangsberg D, et al
. Socioeconomic status, access to triple therapy, and survival from HIV-disease since 1996.AIDS
30. Andersen R, Bozzette S, Shapiro M, St Clair P, Morton S, Crystal S, et al
. Access of vulnerable groups to antiretroviral therapy among persons in care for HIV disease in the United States. HCSUS Consortium. HIV Cost and Services Utilization Study.Health Serv Res
31. McKinney MM, Marconi KM. Delivering HIV services to vulnerable populations: a review of CARE Act-funded research.Public Health Rep
32. Dray-Spira R, Lert F. Social health inequalities during the course of chronic HIV disease in the era of highly active antiretroviral therapy.AIDS
33. Moore RD, Stanton D, Gopalan R, Chaisson RE. Racial differences in the use of drug therapy for HIV disease in an urban community.N Engl J Med
34. Ickovics JR, Forsyth B, Ethier KA, Harris P, Rodin J. Delayed entry into health care for women with HIV disease.AIDS Patient Care STDS
35. Shapiro MF, Morton SC, McCaffrey DF, Senterfitt JW, Fleishman JA, Perlman JF, et al
. Variations in the care of HIV-infected adults in the United States: results from the HIV Cost and Services Utilization Study.JAMA
36. Anderson KH, Mitchell JM. Differential access in the receipt of antiretroviral drugs for the treatment of AIDS and its implications for survival.Arch Intern Med
37. Cook JA, Cohen MH, Grey D, Kirstein L, Burke J, Anastos K, et al
. Use of highly active antiretroviral therapy in a cohort of HIV-seropositive women.Am J Public Health
38. Hsu LC, Vittinghoff E, Katz MH, Schwarcz SK. Predictors of use of highly active antiretroviral therapy (HAART) among persons with AIDS in San Francisco, 1996
–1999.J Acquir Immune Defic Syndr
39. Wood E, Low-Beer S, Bartholomew K, Landolt M, Oram D, O'Shaughnessy MV, et al
. Modern antiretroviral therapy improves life expectancy of gay and bisexual males in Vancouver's West End.Can J Public Health
40. Bassetti S, Battegay M, Furrer H, Rickenbach M, Flepp M, Kaiser L, et al
. Why is highly active antiretroviral therapy (HAART) not prescribed or discontinued? Swiss HIV Cohort Study.J Acquir Immune Defic Syndr
41. Dorrucci M, Pezzotti P, Phillips AN, Alliegro MB, Rezza G. Antiretroviral treatment and progression to AIDS in HIV seroconverters from different risk groups. HIV Italian Seroconversion Study.AIDS
42. Murri R, Fantoni M, Del Borgo C, Izzi I, Visona R, Suter F, et al
. Intravenous drug use, relationship with providers, and stage of HIV disease influence the prescription rates of protease inhibitors.J Acquir Immune Defic Syndr
43. Carrieri MP, Moatti JP, Vlahov D, Obadia Y, Reynaud-Maurupt C, Chesney M. Access to antiretroviral treatment among French HIV infected injection drug users: the influence of continued drug use. MANIF 2000 Study Group.J Epidemiol Commun Health
44. Celentano DD, Vlahov D, Cohn S, Shadle VM, Obasanjo O, Moore RD. Self-reported antiretroviral therapy in injection drug users.JAMA
45. Strathdee SA, Palepu A, Cornelisse PG, Yip B, O'Shaughnessy MV, Montaner JS, et al
. Barriers to use of free antiretroviral therapy in injection drug users.JAMA
46. Gupta SB, Gilbert RL, Brady AR, Livingstone SJ, Evans BG. CD4 cell counts in adults with newly diagnosed HIV infection: results of surveillance in England and Wales, 1990
–1998. CD4 Surveillance Scheme Advisory Group.AIDS
47. Egger M, May M, Chene G, Phillips AN, Ledergerber B, Dabis F, et al
. Prognosis of HIV-1-infected patients starting highly active antiretroviral therapy: a collaborative analysis of prospective studies.Lancet
48. Kahn JG, Zhang X, Cross LT, Palacio H, Birkhead GS, Morin SF. Access to and use of HIV antiretroviral therapy: variation by race/ethnicity in two public insurance programs in the U.S.Public Health Rep
49. Celentano DD, Galai N, Sethi AK, Shah NG, Strathdee SA, Vlahov D, et al
. Time to initiating highly active antiretroviral therapy among HIV-infected injection drug users.AIDS
50. Samet JH, Retondo MJ, Freedberg KA, Stein MD, Heeren T, Libman H. Factors associated with initiation of primary medical care for HIV-infected persons.Am J Med
51. Swindells S, Cobos DG, Lee N, Lien EA, Fitzgerald AP, Pauls JS, et al
. Racial/ethnic differences in CD4 T cell count and viral load at presentation for medical care and in follow-up after HIV-1 infection.AIDS
52. Fairfield KM, Libman H, Davis RB, Eisenberg DM. Delays in protease inhibitor use in clinical practice.J Gen Intern Med
53. Ahdieh Grant L, Silverberg MJ, Palacio H, Minkoff H, Anastos K, Young MA, et al
. Discontinuation of potent antiretroviral therapy: predictive value of and impact on CD4 cell counts and HIV RNA levels.AIDS
54. d'Arminio Monforte A, Lepri AC, Rezza G, Pezzotti P, Antinori A, Phillips AN, et al
. Insights into the reasons for discontinuation of the first highly active antiretroviral therapy (HAART) regimen in a cohort of antiretroviral naive patients. I.CO.N.A. Study Group. Italian Cohort of Antiretroviral-Naive Patients.AIDS
55. Palepu A, Yip B, Miller C, Strathdee S, O'Shaughnessy MV, Montaner JS, et al
. Factors associated with the response to antiretroviral therapy among HIV-infected patients with and without a history of injection drug use.AIDS
56. Hogg RS, Heath KV, Bangsberg D, Yip B, Press N, O'Shaughnessy MV, et al
. Intermittent use of triple combination therapy is predictive of mortality at baseline and after one year of follow-up.AIDS
57. Wood E, Hogg RS, Yip B, Harrigan PR, O'Shaughnessy MV, Montaner JS. Is there a baseline CD4 cell count that precludes a survival response to modern antiretroviral therapy?AIDS
58. Bangsberg D, Tulsky JP, Hecht FM, Moss AR. Protease inhibitors in the homeless.JAMA
59. Hammett TM, Harmon MP, Rhodes W. The burden of infectious disease among inmates of and releasees from US correctional facilities, 1997.Am J Public Health
60. Buchanan D, Khoshnood K, Stopka T, Shaw S, Santelices C, Singer M. Ethical dilemmas created by the criminalization of status behaviors: case examples from ethnographic field research with injection drug users.Health Educ Behav
61. Grund JP, Blanken P, Adriaans NF, Kaplan CD, Barendregt C, Meeuwsen M. Reaching the unreached: targeting hidden IDU populations with clean needles via known user groups.J Psychoactive Drugs
62. Bluthenthal RN, Lorvick J, Kral AH, Erringer EA, Kahn JG, et al
. Collateral damage in the war on drugs: HIV risk behaviours among injection drug users.Int J Drug Policy
63. Bluthenthal RN, Kral AH, Lorvick J, Watters JK. Impact of law enforcement on syringe exchange programs: a look at Oakland and San Francisco.Med Anthropol
64. Wainberg MA, Friedland G. Public health implications of antiretroviral therapy and HIV drug resistance.JAMA
65. Bogart LM, Kelly JA, Catz SL, Sosman JM. Impact of medical and nonmedical factors on physician decision making for HIV/AIDS antiretroviral treatment.J Acquir Immune Defic Syndr
66. Bangsberg DR, Hecht FM, Charlebois ED, Zolopa AR, Holodniy M, Sheiner L, et al
. Adherence to protease inhibitors, HIV-1 viral load, and development of drug resistance in an indigent population.AIDS
67. Sollitto S, Mehlman M, Youngner S, Lederman MM. Should physicians withhold highly active antiretroviral therapies from HIV-AIDS patients who are thought to be poorly adherent to treatment?AIDS
68. Bangsberg DR, Moss A. When should we delay highly active antiretroviral therapy?J Gen Intern Med
69. Bangsberg DR, Hecht FM, Clague H, Charlebois ED, Ciccarone D, Chesney M, et al
. Provider assessment of adherence to HIV antiretroviral therapy.J Acquir Immune Defic Syndr
70. Miller LG, Liu H, Hays RD, Golin CE, Beck CK, Asch SM, et al
. How well do clinicians estimate patients’ adherence to combination antiretroviral therapy?J Gen Intern Med
71. Gross R, Bilker WB, Friedman HM, Coyne JC, Strom BL. Provider inaccuracy in assessing adherence and outcomes with newly initiated antiretroviral therapy.AIDS
72. Lucas GM, Chaisson RE, Moore RD. Highly active antiretroviral therapy in a large urban clinic: risk factors for virologic failure and adverse drug reactions.Ann Intern Med
73. Gallego Deike L, Gordillo Alvarez-Valdes MV. Mental disorders in patients infected with the human immunodeficiency virus.An Med Interna
74. Safren SA, Otto MW, Worth JL, Salomon E, Johnson W, Mayer K, et al
. Two strategies to increase adherence to HIV antiretroviral medication: life-steps and medication monitoring.Behav Res Ther
75. Murphy DA, Lu MC, Martin D, Hoffman D, Marelich WD. Results of a pilot intervention trial to improve antiretroviral adherence among HIV-positive patients.J Assoc Nurses AIDS Care
76. Broadhead RS, Heckathorn DD, Altice FL, van Hulst Y, Carbone M, Friedland GH, et al
. Increasing drug users’ adherence to HIV treatment: results of a peer-driven intervention feasibility study.Soc Sci Med
77. Frieden TR, Fujiwara PI, Washko RM, Hamburg MA. Tuberculosis in New York City – turning the tide.N Engl J Med
78. Chaisson RE, Barnes GL, Hackman J, Watkinson L, Kimbrough L, Metha S, et al
. A randomized, controlled trial of interventions to improve adherence to isoniazid therapy to prevent tuberculosis in injection drug users.Am J Med
79. Bangsberg DR, Mundy LM, Tulsky JP. Expanding directly observed therapy: tuberculosis to human immunodeficiency virus.Am J Med
80. Liechty C, Bangsberg D. Doubts about DOT: Antiretroviral therapy for resource poor settings.AIDS
: in press.
81. Mitty JA, Stone VE, Sands M, Macalino G, Flanigan T. Directly observed therapy for the treatment of people with human immunodeficiency virus infection: a work in progress.Clin Infect Dis
82. Fischl M, Rodriguez A, Scerpella E, Mondroig R, Thompson L, Rechtine D. Directly observed therapy on outcomes in HIV clinical trials.Seventh Conference on Retroviruses and Opportunistic Infections (CROI
). San Francisco, 2000.
83. Altice FL, Mostashari F, Friedland GH. Trust and the acceptance of and adherence to antiretroviral therapy.J Acquir Immune Defic Syndr
84. Gardner LI, Holmberg SD, Moore J, Arnsten JH, Mayer KH, Rompalo A, et al
. Use of highly active antiretroviral therapy in HIV-infected women: impact of HIV specialist care.J Acquir Immune Defic Syndr
85. McCally M, Haines A, Fein O, Addington W, Lawrence RS, Cassel CK. Poverty and ill health: physicians can, and should, make a difference.Ann Intern Med
86. Antela A, Casado JL, Gonzalez MJ, Perez P, Perez-Elias MJ, Montilla P, et al
. Influence of a methadone maintenance programme on the improved outcome of a cohort on injecting drug users with advanced HIV disease.AIDS
87. Moreno A, Perez-Elias MJ, Casado JL, Munoz V, Antela A, Dronda F, et al
. Long-term outcomes of protease inhibitor-based therapy in antiretroviral treatment-naive HIV-infected injection drug users on methadone maintenance programmes.AIDS
88. Wenger LD, Rosenbaum M. Drug treatment on demand–not.J Psychoactive Drugs
89. Johnson RE, Chutuape MA, Strain EC, Walsh SL, Stitzer ML, Bigelow GE. A comparison of levomethadyl acetate, buprenorphine, and methadone for opioid dependence.N Engl J Med
90. Mino A, Page D, Dumont P, Broers B. Treatment failure and methadone dose in a public methadone maintenance treatment programme in Geneva.Drug Alcohol Depend
91. Perneger TV, Giner F, del Rio M, Mino A. Randomised trial of heroin maintenance programme for addicts who fail in conventional drug treatments.BMJ
92. Rehm J, Gschwend P, Steffen T, Gutzwiller F, Dobler-Mikola A, Uchtenhagen A. Feasibility, safety, and efficacy of injectable heroin prescription for refractory opioid addicts: a follow-up study.Lancet
93. Brissette S. Medical prescription of heroin–a review.Can HIV AIDS Policy Law Rev
94. Tyndall MW, Craib KJ, Currie S, Li K, O'Shaughnessy MV, Schechter MT. Impact of HIV infection on mortality in a cohort of injection drug users.J Acquir Immune Defic Syndr
95. Tyndall MW, Spittal PM, Laliberte N, Li K, O'Shaughnessy MV, Schechter MT. Intensive injection cocaine use as a primary risk factor of HIV seroconversion among polydrug users in Vancouver.AIDS
96. Bamberger JD, Unick J, Klein P, Fraser M, Chesney M, Katz MH. Helping the urban poor stay with antiretroviral HIV drug therapy.Am J Public Health
97. Sherer R, Stieglitz K, Narra J, Jasek J, Green L, Moore B, et al
. HIV multidisciplinary teams work: support services improve access to and retention in HIV primary care.AIDS Care
98. Riley ED, Wu AW, Junge B, Marx M, Strathdee SA, Vlahov D. Health services utilization by injection drug users participating in a needle exchange program.Am J Drug Alcohol Abuse
99. Wood E, Kerr T, Spittal PM, Small W, Tyndall MW, Li K, et al
. The potential public health and community impacts of safer injecting facilities: Evidence from a cohort of injection drug users.J Acquir Immune Defic Syndr;
100. Alexander CS, Dong W, Schechter MT, O'Shaughnessy MV, Strathdee SA, Mo T, et al
. Prevalence of primary HIV drug resistance among seroconverters during an explosive outbreak of HIV infection among injecting drug users.AIDS
101. Jensen-Fangel S, Pedersen L, Pedersen C, Schade Larsen C, Tauris P, Moller A, et al
. The effect of race/ethnicity on the outcome of highly active antiretroviral therapy for human immunodeficiency virus type 1-infected patients.Clin Infect Dis