This review demonstrates that incomplete engagement in HIV care is common in the United States and that incompletely engaged individuals account for the largest proportion of HIV-infected individuals with detectable viremia. These findings have direct implications for test-and-treat programs, because disengaged individuals continue to contribute to the ongoing transmission of HIV infection. Although improvements in testing for HIV infection and treatment of HIV-infected individuals will be vital for test-and-treat programmatic success, engagement of HIV-infected individuals in care will be critical for individual health and the prevention of HIV transmission to others.
Although nonadherence to antiretroviral therapy and antiretroviral medication resistance were long viewed as barriers to controlling the HIV epidemic, the advent of more potent regimens has shifted the challenge toward earlier steps in the process of recognition and treatment of HIV infection. A new set of clinical and public health strategies are necessary to address this problem, particularly if test-and-treat programs are to be successful. Little is known about the best ways to link and retain HIV-infected individuals in HIV care. A strengths-based case-management intervention was shown to increase 6-month linkage to care, compared with passive referral, from 60% to 78% [31
]. This intervention is widely accepted as the current standard for initial linkage to HIV care, and its results were confirmed in a subsequent community implementation study [72
]. The effect of this intervention on retention in care at 1 year was attenuated, however, and overall, less is known about the best ways to retain individuals in care over time.
Soon after the introduction of potent combination antiretroviral therapy, a series of studies funded through a US Health Resources and Services Administration (HRSA) Special Programs of National Significance (SPNS) found that greater engagement in HIV care was associated with greater use of case-management services, mental health services, substance abuse treatment, transportation assistance, and housing assistance [73
]. Subsequently, HRSA identified case management and outreach as a priority for interventions designed to improve retention in HIV care [74
]. Interventions funded through a subsequent SPNS initiative included behavioral interventions, intensive case management, patient navigation, life skills training, literacy training, and home-based outreach [75
]. As an example of effect size, 4 of the SPNS sites used patient navigation-like interventions, and engagement in care improved from 64% at baseline to 79% at 12 months [76
]. The overall conclusion from the HRSA initiative was that outreach activities held promise for engaging and retaining out-of-care persons in HIV medical care [77
]. Although costly and labor intensive, such interventions exemplify strategies that simultaneously address several of the barriers described here. Such approaches provide the best current hope for comprehensive management.
Additional research on best practices to link and retain HIV-infected individuals in care is needed. Research will need to be multifaceted to approach the problem of poor retention in care from many angles. Interventions targeting HIV-infected populations, such as provision of mental health or substance abuse services, are important but will need to be complemented by more structural interventions that target the system of health care delivery. The latter may be particularly beneficial, because they should be easier to implement, are more sustainable, and might enhance patient-provider relationships, which clearly promotes successful long-term engagement in HIV care [78
]. Patient navigation, intensive case management, cell phone or text-messaging based systems, and integrated informatics to identify at-risk or out-of-care individuals hold promise for further development. Finally, information on the extent to which perceptions of stigma impede engagement in HIV care and interventions should be pursued [79
One of the limitations of this review is that few studies have assessed the extent to which financial barriers impede access to HIV care in the United States. These barriers include lack of insurance coverage, exclusion of HIV infection as a pre-existing condition, and the high costs of care borne by insured individuals through copayment or coinsurance requirements or coverage limitations. The US Government provides financial support for HIV care for low-income individuals through Ryan White–funded programs [81
]. These help support clinical care in many circumstances but do not completely remove the influence and perceived influence of financial barriers on engagement in care. The potential impact of current and future reforms to the US health care system is unknown at this time, but more HIV-infected individuals are likely to qualify for and benefit from coverage under the new system.
Another limitation of this review is the large amount of overlap in the stages of engagement in care. It is difficult to delineate the independent contribution of, for example, poor retention in care, delayed initiation of antiretroviral therapy, and poor adherence to antiretroviral therapy, when the same individuals are prone to deficits in all of these areas. We have made best estimates from available data, but these are further limited by our cross-sectional representation of the longitudinal process of engagement in care. This limitation in our study is also a limitation of the existing literature, which has not clearly described this series of barriers in patient cohorts over time. Finally, this review is focused on the spectrum of engagement in HIV care in the United States and other resource-rich settings. Obstacles to diagnosis of HIV infection, linkage to and retention in HIV care, and receipt of and adherence to antiretroviral therapy in resource-limited settings are of critical importance to the global HIV epidemic and deserve their own review. Although many of the issues may be similar, the magnitude, causes, and solutions may be quite different.
Proponents of a test-and-treat strategy for HIV prevention are aware of the importance and formidable challenge posed by poor engagement in HIV care [4
]. A National Institutes of Health–funded feasibility study called TLC-Plus (Test, Link, and Care-Plus; HIV Prevention Trials Network [HPTN] 065) will assess programs for expanding HIV testing and treatment and linkage to appropriate HIV care and services [83
]. Data from this and other studies will help inform the feasibility of test-and-treat strategies. Although complete eradication of HIV infection through test-and-treat programs is unlikely, incremental improvements in methods to overcome the greatest HIV care challenges today in the United States—undiagnosed HIV infection and inadequate engagement in HIV care—will improve the care of HIV-infected populations and decrease the incidence of HIV infection in the future.