Randomisation was restricted, such that ‘the sum of the covariate values weighted by the number of months in the intervention status must be within cjx100 % of that for control status’, where cj determines how restrictive the criteria was, for six criteria: mean CD4 count, clinic size, average education, tuberculosis treatment levels, existence of a supervised tuberculosis therapy programme, and geography. This evidence concerns the gene CD4 and tuberculosis.