Point-of-Care Diagnosis of Tuberculosis Using a Portable Nucleic Acid Test with Distance-Based Readout.

Rapid and accurate diagnosis of tuberculosis (TB) infection in resource-limited settings is critically needed to stop the spread of the disease but remains difficult to achieve. Herein, we report a fast, inexpensive nucleic acid test with distance-based readout (FINDR) for TB. Based on the unique chromatographic behavior of DNA intercalating dye on unmodified cellulose paper, our FINDR platform converted the amplicons of loop-mediated isothermal amplification (LAMP) into the migration distance on a paper-based analytical device. A suite of innovations were further introduced to enhance the accessibility of FINDR, including (1) screening optimal LAMP primers for distance-based readout; (2) developing a chip-on-cover design capable of streamlining LAMP amplification and distance-based detection in a fully sealed FINDR chip with a simple hand-based swirling for liquid transfer; and (3) integrating FINDR with an upstream portable pipetting-free DNA extractor and a downstream smartphone app to simplify sample processing and data interpretation. With these innovations, FINDR demonstrated a high clinical sensitivity (96.6%) and specificity (100%) upon validation against clinical sputum samples. Successful clinical validation was also achieved when FINDR was deployed as a point-of-care test for detecting TB under resource-limited conditions.