CD4 and tuberculosis: The model that performed best in our iterations contained the following variables: sputum smear grade; new/previous history of ATT; disease classification (pulmonary versus extra-pulmonary); HIV status, ART status, and CD4 cell count at the time of TB diagnosis; sex and age (with interaction terms between age and sex; sputum smear status and type of TB; HIV status at TB diagnosis and CD4 cell category).