Tryptophan and Its derived Metabolites as Biomarkers for Tuberculosis Disease: A Systematic Review

Background: Feasible diagnostic assays are required to detect new TB cases and monitor treatment. Utilizing host biomarker-based data obtained from non-sputum samples could meet the criteria outlined in the TPP for pointof-care testing. The aim of this study was to evaluate evidence on Trp and its metabolites as proposed biomarkers for TB. Methods: We conducted a systematic review on Trp and its metabolites as potential biomarkers. Through specific keyword searches, we identified 170 relevant literature sources and ultimately included seven publications spanning from 2013 to 2023. The biomarker used in these studies were IDO activity, IDO-1 gene expression, and plasma IDO protein, which were measured using techniques such as ELISA, LC-MS, UPLC, and transcriptional profiling. The studies encompassed a pediatric case-control study and six studies involving adults, pregnant women with TB-HIV, individuals with MDR-TB, and individuals with active TB and latent TB. Results: The assessment of IDO activity and IDO proteins level demonstrated promising performance in distinguishing active TB from controls, as well as in evaluating treatment failure and recurrent cases to controls. Trp and its metabolites fulfilled nearly all of TPP criteria for detecting active TB. Conclusion: This study highlights the potential of utilizing host Trp and its metabolites as non-sputum-based biomarker for TB infection. DOI: 10.61186/ibj.4174