CD4 and HIV infectious disease: An average of 12 years standard deviation and 8 years [mean, standard deviation, 8 years] of known HIV infection was encountered in HIV-positive individuals, with median CD4 cell counts of 52 (quartile 1 = 52, quartile 2 = 210) and 462 (quartile 1 = 270, quartile 2 = 640) per μL, respectively.