TOI-IGRA: A Fingertip Blood Biosensing Technology for Decentralized Quantification of Pathogen-Specific T-Cell Responses

T-cell immune responses are key components of the adaptive immune system. The Interferon-γ Release Assay (IGRA), a standardized method for evaluating T-cell function, is widely used for tuberculosis (TB) diagnosis. However, conventional IGRA requires venous blood (approximately 5 mL), involves lengthy processing (around 24 h), and relies on burdensome workflows, limiting its applicability in decentralized or resource-limited settings. Here, we present TOI-IGRA, a fingertip blood-based T-cell functional assay built on our in-house Tip Optofluidic Immunoassay (TOI) platform. Requiring only 15-25 μL of capillary blood, TOI-IGRA offers a minimally invasive, rapid, and efficient renovation to the standard IGRA. We demonstrate that fingertip blood yields comparable T-cell functional results with venous blood, and clinical validation in TB patients confirmed diagnostic performance equivalent to that of the standard IGRA. Furthermore, the TOI-IGRA concept can be extended to assess T-cell responses against other pathogens, including SARS-CoV-2. The platform also enables concurrent quantitative analysis of pathogen-specific T-cell responses and binding antibodies from the same fingertip blood sample. With its minimal blood requirement, operational simplicity, and versatility, TOI-IGRA represents a powerful tool for decentralized diagnostics, large-scale immune surveillance, and personalized vaccine monitoring across diverse healthcare settings.