Abstract

Objective: Inadequate adherence to highly active antiretroviral therapy (HAART) may lead to poor health outcomes and the development of HIV strains that are resistant to HAART. The authors developed a model to evaluate the cost-effectiveness of counseling interventions to improve adherence to HAART among men who have sex with men (MSM). Methods. The authors developed a dynamic compartmental model that incorporates HIV treatment, adherence to treatment, and infection transmission and progression. All data estimates were obtained from secondary sources. The authors evaluated a counseling intervention given prior to initiation of HAART and before all changes in drug regimens, combined with phone-in support while on HAART. They considered a moderate-prevalence and a high-prevalence population of MSM. Results. If the impact of HIV transmission is ignored, the counseling intervention has a cost-effectiveness ratio of $25,500 per quality-adjusted life year (QALY) gained. When HIV transmission is included, the cost-effectiveness ratio is much lower: $7400 and $8700 per QALY gained in the moderate- and high-prevalence populations, respectively. When the intervention is twice as costly per counseling session and half as effective as estimated in the base case (in terms of the number of individuals who become highly adherent, and who remain highly adherent), then the intervention costs $17,100 and $19,600 per QALY gained in the 2 populations, respectively. Conclusions. Counseling to improve adherence to HAART increased length of life, modestly reduced HIV transmission, and cost substantially less than $50,000 per QALY gained over a wide range of assumptions but did not reduce the proportion of drug-resistant strains. Such counseling provides only modest benefit as a tool for HIV prevention but can provide significant benefit for individual patients at an affordable cost.

ABSTRACT

Control of infectious diseases is a key global health priority. This paper describes the role that simulation can play in evaluating policies for infectious disease control. We describe ongoing simulation studies in three different areas: HIV prevention and treatment, contact tracing, and hepatitis B prevention and control.

We evaluated the frequency of HIV testing across the Department of Veterans Affairs (VA), the largest provider of HIV care in the United States. An electronic survey was used to determine the volume and location of HIV screening, confirmatory testing, rapid testing and laboratory consent policies in VA medical centers between October 1, 2005, and September 30, 2006. One hundred thirty-five VA laboratories reported that 112,033 HIV screening tests were performed (81% outpatients vs. 19% inpatients, p<.0001). Overall HIV prevalence was 1.49% (1.62% in inpatients vs. 1.46% in outpatients, p=N.S., range=0.2-3.8%). Rapid testing was available in 67% of facilities, 60% of which took place in the clinical laboratory. Sixty-four percent of labs required a copy of the informed consent in order to perform testing. We estimate that fewer than 10% of VA inpatients and fewer than 5% of VA outpatients were tested for HIV during the survey period. Substantial opportunities for increasing routine HIV testing exist in this population.

Although HIV infection is more prevalent in people younger than age 45 years, a substantial number of infections occur in older persons. Recent guidelines recommend HIV screening in patients age 13 to 64 years. The cost-effectiveness of HIV screening in patients age 55 to 75 years is uncertain. OBJECTIVE: To examine the costs and benefits of HIV screening in patients age 55 to 75 years. DESIGN: Markov model. DATA SOURCES: Derived from the literature. TARGET POPULATION: Patients age 55 to 75 years with unknown HIV status. TIME HORIZON: Lifetime. PERSPECTIVE: Societal. INTERVENTION: HIV screening program for patients age 55 to 75 years compared with current practice. OUTCOME MEASURES: Life-years, quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness. RESULTS OF BASE-CASE ANALYSIS: For a 65-year-old patient, HIV screening using traditional counseling costs $55,440 per QALY compared with current practice when the prevalence of HIV was 0.5% and the patient did not have a sexual partner at risk. In sexually active patients, the incremental cost-effectiveness ratio was $30,020 per QALY. At a prevalence of 0.1%, HIV screening cost less than $60,000 per QALY for patients younger than age 75 years with a partner at risk if less costly streamlined counseling is used. RESULTS OF SENSITIVITY ANALYSIS: Cost-effectiveness of HIV screening depended on HIV prevalence, age of the patient, counseling costs, and whether the patient was sexually active. Sensitivity analyses with other variables did not change the results substantially. LIMITATIONS: The effects of age on the toxicity and efficacy of highly active antiretroviral therapy and death from AIDS were uncertain. Sensitivity analyses exploring these variables did not qualitatively affect the results. CONCLUSION: If the tested population has an HIV prevalence of 0.1% or greater, HIV screening in persons from age 55 to 75 years reaches conventional levels of cost-effectiveness when counseling is streamlined and if the screened patient has a partner at risk. Screening patients with advanced age for HIV is economically attractive in many circumstances.