AIDS, Sexual Behavior, and Intravenous Drug Use (1989) / Chapter Skim
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Cost-Effectiveness Analysis of AIDS Prevention Programs: Concepts, Complications, and Illustrations
Cost-Effectiveness Analysis of AIDS Prevention Programs: Concepts, Complications, and Illustrations
Pages 471-499
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From page 471... ...
Screening of high-risk groups, such as homosexual men, intravenous (IV) drug users, and visitors to sexually transmitted disease clinics, as well as screening of more heterogeneous population segments at a time at which transmission would be especially likely for example, couples entering marriage and blood donors have all been advocated.
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From page 472... ...
Programs to limit HIV spread among needIe-sharing drug users, such as bleach distribution by outreach workers or needle exchange, are also very much under consideration. Another type of prevention program is contact tracing, which has been used with some success in dealing with other sexually transmitted diseases.
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From page 473... ...
A COST-EFFECTIVENESS MODEL FOR AIDS PREVENTION The purpose of applying cost-effectiveness analysis to AIDS prevention programs is to guide the setting of priorities for the use of finite resources, with the objective of achieving the maximum reduction in AIDS-related mortality and morbidity. The cost-effectiveness model user!
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From page 474... ...
ASSESSING PROGRAM EFFECTIVENESS Measures of Health Outcome Various measures of outcome can be used to assess the effectiveness of prevention programs directed at AIDS. These include both measures of final outcome and intermediate outcome measures.
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From page 475... ...
One further complication of using discounted life-years saved as an outcome measure is that life expectancy may vary for groups of the same age, depending upon how groups are defined. This is an important concern in evaluating the effectiveness of AIDS prevention programs.
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From page 476... ...
One may, therefore, not believe it is appropriate to "penalize" drug users for suffering from a disease over which they may have limited control. Intermediate Outcome Measures Whereas final outcome measures reflect ultimate program goals, the effect of a given program on discounted life-years or QALYs saved is often difficult to assess.
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From page 477... ...
Intermediate outcome measures of the effectiveness of these programs may describe the frequency of condom use before and after an educational campaign or the numbers of partners before and after the circulation of a "safer sex" pamphlet. The importance of these and other behavioral changes, however, depends on how these results actually translate into prevention of AIDS cases.
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From page 478... ...
(For example, HIV prevalence could vary considerably between populations of marriage candidates and populations of blood donors, although preliminary data from the premarital testing program in Illinois are consistent with prevalence estimates basest on blood donors.) Other variables (e.g., probability of transmission by sexual contact with and without protection)
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From page 479... ...
The aggregate gain in life expectancy attributable to preventing a case of HIV infection in a relatively Tow-prevaTence population of drug users (as in Houston, where HIV prevalence among IV drug users is estimated at 3 percent) is greater than that attributable to preventing a case in New York City (where HIV prevalence among IV drug users exceeds 50 percent)
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From page 480... ...
An important insight from this reasoning is that the most costeffective communities in which to implement AIDS prevention programs may be those with intermediate levels of HIV prevalence. If prevalence is too Tow, resources are squandered in preventing very Tow probability events.
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From page 481... ...
Therefore, in the absence of empirical data, modeling remains the only viable approach to exploring the implications of heterogeneity. COLLATERAL PROGRAM EFFECTS An important issue in applying cost-effectiveness analysis to AIDS prevention programs is the appropriate treatment of collateral program effects.
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From page 482... ...
The goal of drug treatment abstinence from IV drug use is unquestionably the most effective means of eliminating the possibility of contracting AIDS by sharing needles. However, transmission of HIV among drug users can also be reduced or prevented by much less expensive means.
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From page 483... ...
home care, less frequent and earlier hospitalization, and decreased reliance on diagnostic tests will help to lower average costs. These variations are important in estimating net programs in different geographical areas.
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From page 484... ...
be weighted according to society's valuation of the "quality" of these years compared to the years of a non-(lrug user's life. Alternatively, by using the actual -life expectancy of IV drug users in calculating the number of years of-life saved, instead of national averages by age and sex, the value of these lives could be reduced.
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From page 485... ...
The health outcome measure employed here is the gain in quaTityadjusted life-years, including gain in life expectancy and quality of life due to prevention of AIDS cases, as well as Toss in quality of life due to anxiety among false positives. Prevention of the birth of HTVinfected children is not assigned either a positive or a negative value, although the direct cost savings associated with their treatment are incorporated into the calculation of net resource cost.
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From page 486... ...
Probability of maternal-fetal transmission: 0.50 (7) Latency distribution of AIDS onset from time of HIV infection, basest on San Ffancisco Hepatitis B Cohort Study, with extrapolation according to a Weibull probability distribution; data consistent with median latency of approximately ~ years8 1(la)
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From page 487... ...
Cost of counseling: $25 (13c) Cost of Western blot test (for ETA positives)
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From page 488... ...
The meaning of this level of cost-effectiveness in the context of AIDS prevention must await analogous evaluations of other programs that compete for society's limited resources. Moreover, sensitivity analyses are required to test the stability of this ratio compared to analogous ratios for other AIDS prevention programs, with resulting implications for field research.
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From page 489... ...
In light of all of the above, the potential role of condom use as an AIDS prevention strategy among teenagers needs to be analyzecI. A complete cost-benefit analysis of condom promotion anti distribution programs is not attempted in this paper.
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From page 490... ...
To compute the cumulative probability of becoming infected during four years of adolescence, the following hypothetical values of the inputs are used:
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From page 491... ...
Given the hypothetical values for the inputs, condom use appears to be a highly effective AIDS prevention strategy. Among teenagers who are not very sexually active (e.g., m = 2, n = 10)
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From page 492... ...
is larger among heterosexual adolescents than among homosexuals. Sensitivity Analysis of HIV Prevalence and Condom Efficacy To determine how confident one should be about condom effectiveness, sensitivity analysis was performed by increasing the value of p (HIV prevalence)
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From page 493... ...
aValues in parentheses are percent reductions from the cumulative probability of HIV infection under the baseline assumption of zero condom use.
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From page 494... ...
If e = 0.9 and p = 0.2, half-time and full-time condom use cut the risk by 40-50 and 86-90 percent, respectively, again depending upon the sexual activity assumptions. Because it is unlikely that any adolescent population is currently at p = 0.2 and it is likely that e > 0.5, condom use appears to be a promising strategy for reducing the risk of HIV infection among aclolescents.
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From page 495... ...
Accounting for Heterogeneity of HIV Prevalence So far all members of the population at risk have been assumed to select partners from the same HIV "prevalence pool." Suppose instead
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From page 496... ...
The relative effectiveness of condom use uncler these circumstances must then be determinecl. To determine the cumulative probability of infection with three pools of HIV prevalence, 3 P = 1—~vj{pj[1—r(1—fe)
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From page 497... ...
(13) TABLE 4 Cumulative Probability of HIV Infection if Three "Prevalence Pools" Are Assumed, Given Mean Prevalence of 0.015, Alternative Rates of Condom Use, and Specified Sexual Behavior Pattern (n = 100, m = 5)
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From page 498... ...
The cumulative risk of infection is 0.65 from 10 "protected" exposures, 0.93 from 25 exposures, 0.995 from 50 exposures, and 0.99997 from 100 exposures. In a potential population of partners that is known to include such superinfectors, TABLE 5 Cumulative Probability of HIV Infection Under Alternative Assumptions About the Fraction of Partners in Various Transmissibility Groups ("superinfector" case)
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