CD4 and tuberculosis: The sputum specimens in the China study, that has closer prevalence with the present study, were collected from patients with CD4 counts < 350 cells/mm3, and had slightly different methods: the TB symptom screening methods used were before the current four symptom TB screen was recommended by WHO and the culture methods used was on a BacT/Alert 3D Microbial Detection System (bioMerieux, Craponne, France).