The meta-analysis of these four studies found that antiretroviral therapy is strongly associated with a reduction in tuberculosis incidence in adults with baseline CD4 counts from 200 to 350 cells/μl (HR 0.34, 95% CI 0.19 to 0.60; p-value for effect <0.001; p-value for heterogeneity = 0.069). Here, CD4 is linked to tuberculosis.