For slope models this included, gender, baseline age, baseline CD4 count, baseline WHO stage, ART initiating or ‘baseline’ regimen, e.g. efavirenze vs nevirapine, baseline exposure to zidovudine or stavudine, ART duration, log-VL, baseline hemoglobin level, baseline Body Mass Index (BMI), year of ART start, study site and tuberculosis incidence. Here, CD4 is linked to tuberculosis.