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Miguel Goicoechea, Richard Haubrich, CD4 Lymphoctye Percentage versus Absolute CD4 Lymphocyte Count in Predicting HIV Disease Progression: An Old Debate Revisited, The Journal of Infectious Diseases, Volume 192, Issue 6, 15 September 2005, Pages 945–947, https://doi.org/10.1086/432972
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Even before the first effective antiretroviral therapy (ART) became available nearly 20 years ago, various staging systems were used to predict HIV disease progression, and, subsequently, these systems have been used to guide initiation of therapy. They are based on measurements of CD4 lymphocytes, including the absolute CD4 lymphocyte count, the percentage of lymphocytes that are CD4 positive (CD4 lymphocyte percentage), and the CD4:CD8 lymphocyte ratio [1]. In this issue of the Journal of Infectious Diseases Hulgan et al. [2] present data that suggest that the baseline CD4 lymphocyte percentage may be an additional predictor of disease progression in a subset of individuals who have absolute CD4 lymphocyte counts >350 cells/mm3 but have low CD4 lymphocyte percentages. Although absolute CD4 lymphocyte counts and CD4 lymphocyte percentages provide similar information and are highly correlated, these correlations are not perfect; in one study, the correlation coefficient between the 2 markers was 0.5 [1]. Differences between absolute CD4 lymphocyte count and CD4 lymphocyte percentage may represent a type of immune discordance. A relatively high absolute CD4 lymphocyte count and a low CD4 lymphocyte percentage may occur in 8%–10% of untreated HIV-infected patients [3, 4]. This has potentially important clinical implications. Current guidelines for initiation of therapy for asymptomatic individuals with HIV RNA levels <100,000 copies/mL are based on the absolute CD4 lymphocyte count and recommend initiating ART at a count ⩽350 cells/mm3 [5, 6]. For minimally symptomatic patients, a CD4 lymphocyte count <200 cells/mm3 is used as a guide in resource-limited settings [7]. Given that response to therapy is dependent on disease stage, if a significant number of HIV-infected patients present with this type of discordance, it may partially explain why some individuals who initiate therapy with moderate disease have suboptimal virologic and immunologic responses [8–10 ]
