Fig. 2

Causal directed acyclic graph linking tuberculosis (the exposure) to atopy (the outcome). exposure (Tuberculosis), outcome (Atopy), ancestor of exposure, ancestor of outcome, ancestor of exposure and outcome, adjusted variable, causal path, unobserved (latent), biasing path. Adjustment for confounders (ancestors of both the exposure and the outcome). Age, Crowding Index, Gender. These 3 co-variates were identified as the minimal sufficient adjustment sets required for estimating the total effect of Atopy on Tuberculosis. These co-variates (age, crowding index and gender) were therefore adjusted for in the multi-variate analysis