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—Log or square root transformation of CD4 values is quite reasonable to assess their relationship to AIDS because the relative hazard increases in a nonlinear way. The effect of such transformation on other predictive markers, however, depends on their mutual relationships. In the three-variable Cox proportional model of our baseline values, the relative hazards of AIDS were 2.59 (95% confidence interval [CI], 1.02 to 6.56) with a decrement of one log in CD4 percentage, 2.46 (95% CI, 1.04 to 5.88) with p24 antigenemia, and 1.77 (95% CI, 1.01 to 3.10) per log10 HIV-1 RNA. Thus, even if there is a marginally better fit of the CD4 values, p24 log10 antigenemia and HIV-1 RNA levels remain independent predictive markers of AIDS risk.
Henrard DR, Goedert J. Percentage of CD4 Lymphocytes and Risk of AIDS-Reply. JAMA. 1995;274(23):1836. doi:10.1001/jama.1995.03530230022017