Data from the North America-AIDS Cohort Collaboration on Research and Design (NA-ACCORD) clearly demonstrated that the adjusted mortality rates were statistically higher among the 6,935 patients who deferred therapy until their CD4 counts fell to <500 cells/μl than in the 2,200 patients who started therapy with CD4 counts >500 cells/μl (risk ratio: 1.94, 95% CI: 1.37 to 2.79). This evidence concerns the gene CD4 and AIDS.