Eligibility criteria for down-referral to GPs included being initiated on, and remaining on a standard first-line ART regimen according to the prevailing South African HIV treatment guidelines for at least 12 months at the referring site, a viral load of < 400 copies/ml, CD4 count of > 250 cells/μl, no comorbidities and not on treatment for tuberculosis (TB) at down-referral. This evidence concerns the gene CD4 and tuberculosis.