Microscale Multiplexed Antigen-Specific Antibody Fc Profiling for Point-of-Care Diagnosis of Tuberculosis

Accurate, affordable tuberculosis (TB) diagnostics that do not require sputum samples are urgently needed for TB control and elimination. Prior serological TB tests have failed due to low accuracy in diagnosing active TB (ATB) in endemic areas where baseline seropositivity, due to latent infection (LTBI) or vaccination, is common. We combined high-throughput sample-sparing antibody-omics with machine learning to profile Fab and Fc features of Mycobacterium tuberculosis (Mtb)-specific antibodies in plasma from adults with ATB or latent infection (LTBI). A five-feature Fc-centric signature dominated by enhanced FcγR3B binding, distinguished ATB from LTBI (AuRoC>0.9). To translate this signature for point-of-care use, we engineered a multimeric, enzyme-labelled FcγR3B probe and integrated it with a microscale silver-metallization assay on a low-cost platform, yielding a cellphone-based optical readout from <10 µL of blood. A further optimized three-feature signature measured on this platform correctly classified ATB from LTBI and endemic controls in two independent cohorts (AuRoC>0.9), exceeding World Health Organization (WHO) target levels for rapid TB triage tests. This work establishes Fc-centric antibody profiling as a viable biomarker discovery route and delivers a multiplexed, sample-sparing, inexpensive test suitable for deployment in resource-limited settings.