|
The potential impact of pre-exposure prophylaxis for HIV prevention among men who have sex with men and transwomen in Lima, Peru: a mathematical modelling study |
Gomez GB, Borquez A, Caceres CF, Segura ER, Grant RM, Garnett GP, Hallett TB |
|
|
Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. CRD summary The objective was to assess the cost-effectiveness of pre-exposure prophylaxis, to prevent HIV infection, in men who have sex with men. The authors concluded that prioritised pre-exposure prophylaxis could be a cost-effective addition to existing HIV prevention strategies. The study methods were adequate, and the results were sufficiently presented. Given the scope of the analysis, the authors’ conclusions appear to be valid. Type of economic evaluation Study objective The objective was to assess the cost-effectiveness of pre-exposure prophylaxis, to prevent HIV infection, in men who have sex with men and in transsexual women, who used to be men. Interventions Pre-exposure prophylaxis, with antiretroviral drugs, was assessed, in four populations. These were men who mostly have sex with women, men who mostly have sex with men, sex workers, and transsexual women (or transvestites) who were at high risk, defined as those who had a large number of male partners. Two scenarios for the scale-up of the prophylaxis programme were investigated: low coverage at 5%; and high coverage at 20%. Coverage could be uniform, across all four groups, or prioritised, with higher coverage for key populations. Pre-exposure prophylaxis was compared with no such treatment. Methods Analytical approach:A deterministic, compartmental model was used to represent the sexual transmission of HIV amongst men who have sex with men and transsexual women in Lima, Peru. The time horizon was 10 years. The authors reported that a health provider perspective was adopted. Effectiveness data:The clinical and effectiveness data were from published studies. The main effectiveness estimates were the effectiveness of prophylaxis in reducing susceptibility to HIV infection, and the proportion of sex acts that were protected. These estimates were from the Pre-Exposure Prophylaxis Initiative (iPrEx; see Other Publications of Related Interest). Monetary benefit and utility valuations:The disability weights for HIV-related conditions were from the Global Burden of Disease study. Measure of benefit:The measure of benefit was disability-adjusted life-years (DALYs) averted. Future benefits were discounted at 3% per year. Cost data:The direct costs included HIV testing (before the intervention, and every three months); HIV confirmatory testing; creatinine or blood urea nitrogen testing; outreach and counselling services; condom and lubricant promotion and provision; and the prophylaxis drugs. The main analysis did not include the costs of HIV treatment after infection resistance testing, or testing and treatment of other sexually transmitted infections. The costs of prophylaxis were from Gilead (manufacturer of antiviral drugs). Information on other costs was from Peruvian published sources. Future costs were discounted at 3% per year. All costs were reported in US $. Analysis of uncertainty:Scenario analyses were undertaken by varying the costs of prophylaxis; the effectiveness of the intervention; and adherence to the intervention. The uncertainty due to the assumptions used was represented by credible intervals. One analysis included the downstream cost savings from antiretroviral treatment averted due to the prevention of HIV, and investigated how prophylaxis might change sexual behaviour and the use of condoms. The cost-effectiveness threshold was defined in two ways. The World Health Organization (WHO) threshold was three times the gross domestic product per capita ($16,203 for Peru). The World Bank threshold was $500. Results For a uniform 5% coverage of prophylaxis, the additional cost per DALY averted was $419 to $4,182, and for 20% coverage, it was $428 to $4,254. For prioritised prophylaxis that achieved 50% coverage for at-risk transsexual women, and 5% coverage across the four populations overall, the additional cost per DALY averted was $159 to $1,596, and for 20% coverage overall, it was $397 to $3,133. For prioritised prophylaxis that achieved 90% coverage for at-risk transsexual women, and 5% coverage across the four populations overall, the additional cost per DALY averted was $163 to $1,553, and for 20% coverage overall, it was $310 to $2,258. At the WHO threshold, all prophylaxis options could be considered cost-effective, but at the World Bank threshold, none of them could be considered cost-effective1. When including the downstream antiretroviral costs averted, prophylaxis became potentially cost-effective, in most scenarios, using the World Bank threshold. 1. Author's comment: None were considered very cost effective but the range of results falls below the WB cost effectiveness threshold for some scenarios. Authors' conclusions The authors concluded that prioritised pre-exposure prophylaxis could be a cost-effective addition to existing HIV prevention strategies, for men who have sex with men. CRD commentary Interventions:The interventions were described, and they appear to have been appropriate comparators; the regimen in the iPrEx clinical trial was compared with the usual practice of no prophylaxis. Effectiveness/benefits:The clinical and effectiveness data were from published studies, but the authors did not report a systematic review to identify them2. As a result it is unclear if all the relevant evidence was included. The main measures of effectiveness were from a clinical trial published in a high-impact journal, and it is likely that these estimates were reliable. DALYs were an appropriate measure of benefit; they capture the burden of disease and allow cross-disease comparisons to be made. The disability weights were from a published study, but the approach used to derive them was not described3. 2. Author's comment: Only one clinical trial (iPrEx) is available regarding the effectiveness of oral pre-exposure prophylaxis among men who have sex with men. 3. Author's comment: This information is available in an appendix to the original paper. Costs:The perspective was explicitly reported to be that of a health provider. The authors stated that some important relevant costs were omitted from their main analysis, including the costs of HIV treatment after infection. This would bias the results against the use of prophylaxis, as savings from HIV cases prevented were omitted. The sensitivity analysis, in which the downstream antiretroviral costs averted were included, showed that prophylaxis was more cost-effective. The authors adequately reported the sources for the cost information. The time horizon, discount rate and currency were reported, but any currency conversions were not. The price year was not reported hampering future inflationary exercises4. 4. Author's comment: All costs are expressed in 2010 $ (this is not explicitly stated, but comparable to the inflation used for the thresholds). Analysis and results:The cost and outcome information was synthesised, using a mathematical model. The details of the model structure were provided, with a diagram. Uncertainty in the results of the model, was tested in scenario analyses, and the results were presented as worst- and best-case scenarios. This type of analysis goes some way in evaluating uncertainty, but a probabilistic sensitivity analysis could have tested the overall model parameter uncertainty5. As a limitation to their study, the authors reported that the model did not consider the possibility of the evolution of drug resistance from individuals using prophylaxis. 5. Author's comment: This was done for the main outputs only as, otherwise, there would have been too much information could have obscured the fundamental results. Concluding remarks:The study methods were adequate, and the results were sufficiently presented. Given the scope of the analysis, the authors’ conclusions appear to be valid. Funding Funding received from the Bill and Melinda Gates Foundation, the Medical Research Council UK, The Wellcome Trust, the US National Institutes of Health, and The Gladstone Institutes. Bibliographic details Gomez GB, Borquez A, Caceres CF, Segura ER, Grant RM, Garnett GP, Hallett TB. The potential impact of pre-exposure prophylaxis for HIV prevention among men who have sex with men and transwomen in Lima, Peru: a mathematical modelling study. PLOS Medicine 2012; 9(10): e1001323 Other publications of related interest Grant RM, Lama JR, Anderson PL, McMahan V, Liu AY, et al. Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. New England Journal of Medicine 2010; 363: 2587-2599. Indexing Status Subject indexing assigned by NLM MeSH Anti-HIV Agents /economics /therapeutic use; Cost-Benefit Analysis; HIV Infections /prevention & Humans; Male; Models, Theoretical; Peru; Unsafe Sex /statistics & control; numerical data AccessionNumber 22012041651 Date bibliographic record published 08/01/2013 Date abstract record published 17/04/2013 |
|
|
|