Fig. 3

Rates of TB incidence over time during and after IPT in the Thibela TB study. (a) intention-to-treat analysis (intended duration of IPT), (b) as-treated analysis (actual duration of IPT) and (c) as-treated analysis among the subset of optimal adherers (>6 months of IPT)). Rates were adjusted for clustering by cluster. P values for overall association between TB incidence and time period of follow-up: (a) <0.001, (b) <0.001 and (c) <0.001. P values for tests for linearity in TB incidence rates over time since IPT cessation: (a) 0.043, (b) 0.633 and (c) 0.077. P values for tests for departure from linearity in TB incidence rates over time since IPT cessation: (a) 0.071, (b) 0.533 and (c) 0.003. CI, Confidence interval; IPT, Isoniazid preventive therapy; pyrs, Person-years