Figure 4.

Summary of the best-fitting impact on the weekly measured tuberculosis disease incidence rate (per 100,000 person-years) during the Thibela TB randomized controlled trial among South African gold miners, 2006–2011. The incidence rate is defined as the incidence that would be observed if it were measured weekly. A) Model predictions obtained by assuming that IPT fully cures all infections and protects against reinfection (IPT assumption 1: 100% cure, 100% protection); B) model is permitted to estimate that 6 months of IPT does not cure all infections and also does not give 100% protection against reinfection during IPT (IPT assumption 3: estimated percentage cured, estimated percentage protection). Note that, for all IPT models, the best-fitting values for the disease rates differed slightly (Web Figure 10), leading to differences in the predicted measured incidence before the introduction of IPT. For each plot, the predicted measured incidence increases in the intervention clusters after the start of the trial because of increased case detection, resulting from screening miners on recruitment into the trial. The cross shows the observed incidence in the intervention arm, aggregated for all intervention clusters; the empty square shows the “observed” incidence in the control arm, taken to equal the incidence in the intervention clusters, divided by 0.98 (the point estimate of the trial impact on incidence). Bars, 95% confidence intervals. IPT, isoniazid preventive therapy; TB, tuberculosis.