CD4 and tuberculosis: However, there is a clear inverse correlation between CD4 count and the risk of opportunistic infections and death.28,29 Markowitz et al.30 identified 2 major risk factors for TB progression: (1) a positive result on a protein purified derivative test at baseline or during the study, which indicates the importance of the degree of previous or current exposure to Mycobacterium tuberculosis, and (2) a low CD4 count, which shows the role of immunodepression in the development of active TB.