Other assays detect host responses to M tuberculosis, including non-specific inflammatory responses (eg, C-reactive protein)19 specific antigen recognition (eg, interferon-gamma response assays, which are mainly useful in diagnosing exposure and infection20), or transcriptomic signatures with some degree of specificity for both tuberculosis and active disease status.21 The sensitivity of tests based on these biomarkers depends on the proportion of people with tuberculosis whose host responses exceed a threshold level. The gene discussed is IFNG; the disease is tuberculosis.