CD4 and tuberculosis: Lower CD4 cell counts are associated with increased risk of mortality [4], [31], [47], [49], [54]–[56] but also with increasing incidence of TB [57]–[60] while the presence of TB disease is associated with reduced CD4 cell counts.[19] Consequently, a lower CD4 cell count not only predicts and increases the risk of mortality but also influences the likelihood of developing TB and can play an intermediate role in the causal effect chain when assessing the impact of TB on mortality.