Transcriptomic Biomarkers for Tuberculosis: Validation of as a Single mRNA Biomarker to Diagnose TB, Predict Disease Progression, and Monitor Treatment Response.

External validation in different cohorts is a key step in the translational development of new biomarkers. We previously described three host mRNA whose expression in peripheral blood is significantly higher () or lower ( and ) in individuals with TB compared to latent TB infection (LTBI) and controls. We have now conducted an independent validation of these genes by re-analyzing publicly available transcriptomic datasets from Brazil, China, Haiti, India, South Africa, and the United Kingdom. Comparisons between TB and control/LTBI showed significant differential expression of all three genes (  < 0.01,   < 0.01, and   < 0.05). had the highest mean area under the ROC curve (AUROC) for the differentiation of TB vs. controls (0.95) and LTBI (0.94). In addition, accurately distinguished TB from the clinically similar conditions pneumonia (AUROC, 0.88), non-active sarcoidosis (0.87), and lung cancer (0.86), but not from active sarcoidosis (0.66). Interestingly, individuals progressing from LTBI to TB showed a constant increase in expression with time when compared to non-progressors ( < 0.05), with a significant change closer to manifestation of active disease (≤3 months, = 0.003). Moreover, expression normalized with completion of anti-TB treatment. Taken together, these results validate mRNA as a diagnostic host biomarker for active TB independent of host genetic background. Moreover, they reveal its potential to predict progression from latent to active infection and to indicate a response to anti-TB treatment.