Identifying skin surface chemicals as potential tuberculosis diagnostic biomarkers using ultra performance liquid chromatography-high resolution mass spectrometry

Tuberculosis (TB) remains a significant cause of morbidity and mortality globally, despite its preventability and curability. Early and accurate diagnosis of active TB is essential for enhancing patient care, improving outcomes, and interrupting the transmission cycles of Mycobacterium tuberculosis (M.tb). Metabolomics proves to be an emerging area of study for the development of a non-invasive approach to TB diagnostics.. High-resolution mass spectrometry combined with ion mobility spectrometry enhances the confidence in identifying and annotating biological markers during metabolomic research. This study outlines an analytical workflow encompassing sample preparation through to multivariate analyses for detecting potential TB diagnostic biomarkers. A custom-designed wearable polydimethylsiloxane (PDMS) sampler was employed as a passive sampling device, effectively concentrating chemical compounds from the skin surface. The sampler was directly desorbed into solvent within an LC vial, streamlining the extraction-to-analysis process. Utilising accurate mass and collision cross sections (CCS), fourteen biomarkers were tentatively identified, demonstrating the ability to differentiate TB patients from control groups. Receiver operating characteristic (ROC) analysis yielded an area under the curve (AUC) of 0.911. Among these, para-aminobenzoic acid (PABA) emerged as a promising biomarker for TB, achieving a specificity of 1, sensitivity of 0.9, and an AUC of 0.961. Method limits of detection for the 1-hour non-invasive skin sampling method ranged from 6 (PABA) to 172 ng (phenylalanine) for a calibration working range of 10 – 800 ng with a R² of ≥ 0.99. These first results demonstrate the potential of using skin surface compounds in TB diagnostics.