Death rates on ART by CD4 count are also confounded by other indications for ART such as the presence of opportunistic infections.100, 101, 102 All combined, there is a much higher level of uncertainty in the HIV/AIDS-specific mortality estimates than in all-cause mortality estimation and these are used as a key covariate in the estimation of all-cause mortality. The gene discussed is CD4; the disease is Opportunistic infection.