{"id":543,"date":"2011-12-15T22:50:55","date_gmt":"2011-12-15T22:50:55","guid":{"rendered":"https:\/\/blogs.bmj.com\/sti\/?p=543"},"modified":"2011-12-15T22:50:55","modified_gmt":"2011-12-15T22:50:55","slug":"modelling-art-impact-on-hiv-prevention-within-discordant-couples","status":"publish","type":"post","link":"https:\/\/blogs.bmj.com\/sti\/2011\/12\/15\/modelling-art-impact-on-hiv-prevention-within-discordant-couples\/","title":{"rendered":"Modelling ART impact on HIV prevention within discordant couples"},"content":{"rendered":"

The HPTN 052 study, discussed in an earlier blog, appears to offer a godsend:\u00a0 a demonstrated 96% reduction in HIV transmission in discordant couples using antiretroviral therapy (ART).\u00a0\u00a0 Apparently, the extension of ART conveys an additional, and unexpected, benefit in its potential impact on prevention.\u00a0 But how do we quantify the additional benefit?<\/p>\n

A recent concise communication in the journal AIDS<\/em> claims that the benefit depends very much on the country you live in.\u00a0 They claim that mathematical modelling can help us pick out the countries where the benefit is greatest \u2013 and consequently most likely to outweigh the various costs and dis-benefits of ART extension.\u00a0 Feed into their model the three factors of population size, HIV prevalence and the percentage of discordant couples, and it will throw up results that common sense would not have predicted \u2013 as, for example, that Malawi, with its potential combination of a reduction in HIV incidence and large number of prevented infections, would benefit more than Ghana, Rwanda or Lesotho (the other countries featuring in the study).<\/p>\n

The most striking finding of this modelling exercise is the importance of the stability of discordant couples. When the model estimates stability at 40% or 70% respectively there is a dramatic change in effectiveness of ART extension as a prevention strategy. \u00a0 \u00a0Even at the higher estimate, however, the prevention of HIV within discordant couples does not result in noticeable decline in national incidence overall, where prevalence is at the levels seen in Rwanda and Ghana. \u00a0This only occurs where incidence reaches higher levels seen in Malawi and Lesotho. Evidently the extension of ART, even to a large proportion of discordant couples, offers no panacea.<\/p>\n

It is possible that a modelling exercise of this kind might enable policy makers to pick out the countries where the benefits of ART extension would be greatest. \u00a0But so far as the countries considered by the paper are concerned (Malawi, Lesotho, Rwanda, Ghana), the presentation of data in this paper is blatantly misleading. \u00a0Why do the authors give equal weight, for each country, to the absolute number of infections prevented <\/em>alongside decline in incidence?\u00a0 What purpose is served by treating the former as an independent factor in determining the benefit derived by each country, when there are such differences in the size of their respective populations? \u00a0We soon discover.\u00a0 The authors\u2019 conclusion that Malawi would derive greater benefit than Lesotho appears to be entirely based on the fact that in the former case the decline in incidence will be accompanied by a much higher number of infections prevented. \u00a0This leaves out of account the relative size of the two populations – and the population of Malawi is almost ten times that of Lesotho!<\/p>\n

Have the authors rushed this paper out in response to the results from \u00a0HPTN 052?<\/p>\n

On HPTN 052:<\/p>\n

http:\/\/www.hptn.org\/web%20documents\/PressReleases\/HPTN052PressReleaseFINAL5_12_118am.pdf<\/a><\/p>\n

Wafaa M. El-Sadr, Brian J. Coburn and Sally M. Blower, \u201cModeling the impact on the HIV epidemic of treating discordant couples with antiretrovirals to prevent transmission\u201d:, AIDS<\/em> Volume 25, issue 18, 28th<\/sup> November 2011<\/p>\n

http:\/\/journals.lww.com\/aidsonline\/Abstract\/2011\/11280\/Modeling_the_impact_on_the_HIV_epidemic_of.12.aspx<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

The HPTN 052 study, discussed in an earlier blog, appears to offer a godsend:\u00a0 a demonstrated 96% reduction in HIV transmission in discordant couples using antiretroviral therapy (ART).\u00a0\u00a0 Apparently, the extension of ART conveys an additional, and unexpected, benefit in its potential impact on prevention.\u00a0 But how do we quantify the additional benefit? A recent […]<\/p>\n

Read More…<\/a><\/p>\n","protected":false},"author":152,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2012,2713],"tags":[],"class_list":["post-543","post","type-post","status-publish","format-standard","hentry","category-hiv-infection","category-modelling"],"yoast_head":"\nModelling ART impact on HIV prevention within discordant couples - Sexually Transmitted Infections<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.bmj.com\/sti\/2011\/12\/15\/modelling-art-impact-on-hiv-prevention-within-discordant-couples\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Modelling ART impact on HIV prevention within discordant couples - Sexually Transmitted Infections\" \/>\n<meta property=\"og:description\" content=\"The HPTN 052 study, discussed in an earlier blog, appears to offer a godsend:\u00a0 a demonstrated 96% reduction in HIV transmission in discordant couples using antiretroviral therapy (ART).\u00a0\u00a0 Apparently, the extension of ART conveys an additional, and unexpected, benefit in its potential impact on prevention.\u00a0 But how do we quantify the additional benefit? 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