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Annals of Internal Medicine
December 20, 2010
"Annual HIV screening and counseling leading to 50% behavior reduction in infected persons, along with 90% ART initiation in symptomatic patients, reduces new infections to fewer than 35 000 per year.....expanding HIV screening and treatment could prevent 200 000 to 300 000 infections over 20 years or approximately 17% to 24% of new infections, adding up to 6.8 million QALYs to the population. To prevent 24% of new infections, routine HIV screening would need to occur annually, with antiretroviral treatment available for essentially all symptomatic patients......Our third finding is that the net benefit of implementing both interventions is greater than the sum from implementing each program individually. A substantial increase in HIV screening or treatment could prevent 95 000 or 198 000 new infections, respectively, whereas a combination program could avert 300 000 infections (an increase of 7000 infections prevented or 2%).....Finally, we find that expanded utilization of ART (to 75% or 90% initiating ART at a CD4 cell count less than 0.350 x 109 cells/L) is very cost-effective, as is 1-time screening of low-risk groups and annual screening of high-risk groups. Combination strategies prevent more HIV infections and increase QALYs more than either individual strategy. As noted, our analysis specifically accounts for the effect of combination screening and treatment on population-wide HIV transmission, which is a strength of our modeling framework. As routine HIV screening for adults increases across health care settings due to recently revised CDC guidelines (3), it is important to ensure that ART utilization increases at a concomitant rate"
Abstract
Background: Although recent guidelines call for expanded routine screening for HIV, resources for antiretroviral therapy (ART) are limited, and all eligible persons are not currently receiving treatment.
Objective: To evaluate the effects on the U.S. HIV epidemic of expanded ART, HIV screening, or interventions to reduce risk behavior.
Design: Dynamic mathematical model of HIV transmission and disease progression and cost-effectiveness analysis.
Data Sources: Published literature.
Target Population: High-risk (injection drug users and men who have sex with men) and low-risk persons aged 15 to 64 years in the United States.
Time Horizon: Twenty years and lifetime (costs and quality-adjusted life-years [QALYs]).
Perspective: Societal.
Intervention: Expanded HIV screening and counseling, treatment with ART, or both.
Outcome Measures: New HIV infections, discounted costs and QALYs, and incremental cost-effectiveness ratios.
Results of Base-Case Analysis: One-time HIV screening of low-risk persons coupled with annual screening of high-risk persons could prevent 6.7% of a projected 1.23 million new infections and cost $22 382 per QALY gained, assuming a 20% reduction in sexual activity after screening. Expanding ART utilization to 75% of eligible persons prevents 10.3% of infections and costs $20 300 per QALY gained. A combination strategy prevents 17.3% of infections and costs $21 580 per QALY gained.
Results of Sensitivity Analysis: With no reduction in sexual activity, expanded screening prevents 3.7% of infections. Earlier ART initiation when a CD4 count is greater than 0.350 x 109 cells/L prevents 20% to 28% of infections. Additional efforts to halve high-risk behavior could reduce infections by 65%.
Limitation: The model of disease progression and treatment was simplified, and acute HIV screening was excluded.
Conclusion: Expanding HIV screening and treatment simultaneously offers the greatest health benefit and is cost-effective. However, even substantial expansion of HIV screening and treatment programs is not sufficient to markedly reduce the U.S. HIV epidemic without substantial reductions in risk behavior.
Primary Funding Source: National Institute on Drug Abuse, National Institutes of Health, and Department of Veterans Affairs.
Approximately 56 000 persons in the United States acquire HIV annually. This number has not decreased in recent years and highlights the need for expanded HIV screening and treatment (1, 2). Routine HIV screening facilitates early identification of HIV infection, linking infected persons with access to life-saving treatments. If accompanied by an effective counseling program, HIV screening may reduce sexual activity and other risky behavior among participants (3-7). Once identified, persons infected with HIV who are eligible to receive antiretroviral therapy (ART) can benefit from substantially reduced mortality and improved quality of life. Moreover, suppressive ART may reduce overall HIV transmission in the population by reducing a recipient's blood plasma viral load and subsequent infectivity (8-14).
Discussion
We aimed to assess the population-wide effects of expanded HIV treatment and screening on the HIV epidemic in the United States. Although previous studies have addressed the effectiveness and cost-effectiveness of either expanded HIV screening (21, 22, 24, 26) or treatment (92-94), they were not designed to fully evaluate how such programs would influence HIV transmission in the overall population or the course of the epidemic. To our knowledge, our study is the first to evaluate the population-wide effects (new HIV infections and other health outcomes) and the cost-effectiveness of alternative combinations of HIV screening and treatment in the United States.
Our study has several key findings. First, we found that expanding HIV screening and treatment could prevent 200 000 to 300 000 infections over 20 years or approximately 17% to 24% of new infections, adding up to 6.8 million QALYs to the population. To prevent 24% of new infections, routine HIV screening would need to occur annually, with antiretroviral treatment available for essentially all symptomatic patients. Our analysis assumes that persons identified as HIV-infected reduce risk behaviors by 20%; even with modest reductions in risk behavior, expansion of screening and treatment would provide enormous health benefits. If persons with HIV reduce risk behavior further, as some studies suggest (7), the health benefit could be substantially higher than we have estimated. Annual HIV screening and counseling leading to 50% behavior reduction in infected persons, along with 90% ART initiation in symptomatic patients, reduces new infections to fewer than 35 000 per year. Even under such optimistic assumptions, the U.S. HIV epidemic is unlikely to be completely eliminated without additional preventive measures.
Second, our analysis highlights the importance of emphasizing risk behavior reduction as HIV screening and treatment becomes increasingly available. For example, in addition to expanded screening and treatment, a 50% reduction in sexual risk behaviors among MSM and needle sharing among injection drug users could prevent 65% of new infections, reducing HIV incidence to approximately 20 000 cases per year. This suggests that programs to reduce risk behavior among high-risk persons will probably be a key component of a successful prevention program. If, however, uninfected persons increase risk behavior after screening, some of the benefits would be attenuated.
Our third finding is that the net benefit of implementing both interventions is greater than the sum from implementing each program individually. A substantial increase in HIV screening or treatment could prevent 95 000 or 198 000 new infections, respectively, whereas a combination program could avert 300 000 infections (an increase of 7000 infections prevented or 2%). Programs to expand screening and treatment will be most effective if they are implemented together, because each program complements the other. Essential to achieving these levels of infections averted is patient receipt of test results after diagnosis, as well as linkage to care, which has been shown to improve with nurse-initiated counseling (95) and health worker follow-up interviews with patients with new diagnoses (96).
The effectiveness of screening and counseling in reducing sexual activity will probably vary among health care settings because of the differences in risk behavior and the length, content, and intensity of counseling services. Even with no reduction in risk behavior, 1-time screening of low-risk groups and annual screening of high-risk groups could prevent nearly 4% of new infections by identifying infected persons and linking them to treatment programs. Augmenting this strategy with expanded ART prevents 16% of new infections. This suggests that preventing future infections through increased ART becomes increasingly important as the effectiveness of screening and counseling diminishes. In settings in which counseling is unavailable or ineffectual, increased utilization of ART can help ensure that expanded screening will lead to reductions in HIV transmission.
Finally, we find that expanded utilization of ART (to 75% or 90% initiating ART at a CD4 cell count less than 0.350 x 109 cells/L) is very cost-effective, as is 1-time screening of low-risk groups and annual screening of high-risk groups. Combination strategies prevent more HIV infections and increase QALYs more than either individual strategy. As noted, our analysis specifically accounts for the effect of combination screening and treatment on population-wide HIV transmission, which is a strength of our modeling framework. As routine HIV screening for adults increases across health care settings due to recently revised CDC guidelines (3), it is important to ensure that ART utilization increases at a concomitant rate. Further expanding HIV screening and counseling services, without expanding the proportion of infected persons receiving ART, does not realize the potential benefits of implementing these 2 complementary interventions.
Compared with other disease screening programs in the United States, 1-time HIV screening of low-risk persons and annual screening of high-risk persons is economically attractive, with a cost-effectiveness ratio less than $23 000 per QALY gained. This compares favorably with other accepted interventions, including screening for type 2 diabetes (97) and breast cancer mammography (98).
Our study has several limitations. First, we assumed proportional mixing among sexual partners and needle-sharing contacts, which simplifies the complex network structure of partnership formation and dissolution. Second, although we stratified the population according to sex and risk behavior, we did not include variations by race or ethnicity. To fully account for such granularity, we would need to accurately estimate sexual and needle-sharing behavior within and between races, which would be difficult to do. Moreover, significant disparities in treatment rates, background mortality, and comorbid conditions exist, and our model cannot account for these additional factors. A third limitation of our study is the omission of acute HIV screening, which would require a different model structure and specific assumptions about the benefits and costs associated with identification and treatment of acute HIV infection. The degree to which acute infection contributes to transmission is uncertain, and estimates vary (47, 99-103). Fourth, we used a simplified HIV treatment model that does not include the intricacies of individual HIV disease management; drug toxicities; CD4 cell count monitoring; or the presence of comorbid conditions, such as coronary heart disease, diabetes, and various types of cancer. Our results, however, are broadly consistent with those from more complicated models of HIV disease progression (21-24, 92, 104). Finally, we did not explicitly model development of resistance to ART, although we believe our assumptions about the benefits of ART are conservative given the introduction of new classes of ART, such as integrase inhibitors and entry inhibitors, and we evaluated scenarios that included resistance in sensitivity analyses.
Expanded HIV screening and counseling in the United States can prevent a substantial number of new HIV infections, adding millions of QALYs to the population. Programs that simultaneously expand ART utilization can prevent more HIV infections than expanding either intervention alone. Our analysis indicates that over the next 2 decades, HIV incidence in the United States could be reduced by 24% with a comprehensive expansion of screening and treatment. If these programs are accompanied by additional interventions that halve risky sexual and needle-sharing behavior, the epidemic could be reduced by 65%, suggesting the need for a comprehensive portfolio of HIV prevention, screening, and treatment.
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