Effective tuberculosis (TB) control requires that people who progress from latent Mycobacterium tuberculosis (MTB) infection (LTBI) to TB disease are identified and treated before they infect others. A prognostic correlate of risk (COR), based on messenger ribonucleic acid (mRNA) expression signatures, which prospectively discriminates between TB cases and healthy controls, has been constructed and validated. Based on published microarray case-control datasets, the COR has 87% diagnostic sensitivity and 97% specificity for prevalent TB disease; and in two nested case-control studies, 70% prognostic sensitivity and 84% specificity for incident TB disease occurring within one year of sampling (HIV uninfected persons). Diagnostic and prognostic performance of the COR has not yet been tested in a prospective cohort.