CD4 and AIDS: The goal of this study was therefore to determine the diagnostic properties (sensitivity, specificity, positive predictive values and negative predictive values) of the WHO HIV/AIDS clinical staging guidelines at CD4<250cells/mm3 and <350cells/mm3 and to determine the WHO HIV/AIDS Stage I and II clinical factors (symptoms and signs) that are predictive of CD4<250cells/mm3 and CD4<350 cells/mm3.