CD4 and tuberculosis: Due to the impact of TB treatment duration and the total CD4+ T cells on the positive rate of T-SPOT.TB assay in HIV combined active tuberculosis infection, we found that the sensitivity of T-SPOT.TB assay could increase to >85% in the patients with TB treatment for less than 1 month and CD4+ T cells ≥200/μl, while the sensitivity for patients treated for more than 3 months and CD4+ T cells < 200/μl was only 33.3% (Figure 5).