National and international guidelines on antiretroviral therapy for HIV infection recently changed to recommend earlier treatment, following the publication during 2009 of two collaborative analyses of HIV cohort studies [1, 2]. These studies used different methodologies, and reached different conclusions about the benefits of very early treatment. I will describe their methods, and possible reasons for differences in their results.
This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.