CD4 and tuberculosis: Some TB household contact studies have found no difference in infectiousness between HIV-positive TB patients compared to HIV-negative TB patients if HIV-positive index cases were less immunosuppressed (CD4 >250 cells/mm3)16 or were smear-positive and/or had cavitary disease.17 Heterogeneity observed in estimates of infectiousness of HIV-positive TB patients compared to HIV-negative TB patients has been well-described, although no studies to date have examined the effect of ART status of the HIV-positive index case.