PROJECT SUMMARY Nearly one-third of the 10 million annual tuberculosis (TB) cases worldwide are missed each year. TB contact tracing is an evidence-based practice that is internationally recommended for finding, treating, and preventing TB among close contacts of TB patients. Contact tracing is also considered a highly significant strategy for advancing the WHO and PAHO goal of eliminating TB in moderate-incidence countries like Colombia by 2050. Unfortunately, large implementation gaps persist. Specifically there is need for 1) better TB screening and testing tools to overcome the low sensitivity of symptom screening and the difficulty of collecting sputum in those without cough, and 2) more client-centered implementation strategies to improve case-finding and linkage to care. In prior work with the Secretariat of Public Health (SPH) in Cali, Colombia, we introduced client-friendly education materials, home sputum collection and transport, and molecular testing for TB. The COVID-19 pandemic has led to further evolution of this service to accommodate telehealth visits, and there is need to further adapt these tools to client expectations and the new digital health landscape. Two of the most promising innovations for achieving these goals are pairing next-generation molecular testing with non-sputum samples like saliva and oral swabs to simplify and improve screening and testing algorithms; and incorporating chat apps (e.g., WhatsApp) and automated customer support tools (i.e., chatbots) as mobile health (mHealth) tools to engage, support, and retain household members. Our scientific approach will be to carry out two cross-sectional studies with nested mixed-methods and design research to refine and adapt these tools for contact tracing. Our overall objectives are to enhance the sensitivity, feasibility, acceptability, and appropriateness of contact tracing, and to prepare for a future household-randomized implementation trial. We propose two specific aims: 1) To determine the diagnostic performance of oral samples for TB molecular testing in possible TB patients in clinic and household settings; and 2) To design and iteratively refine an mHealth strategy for implementing contact tracing optimized for feasibility, acceptability, usability, and appropriateness. The investigative team has expertise in TB diagnostics and clinical care, contact tracing, user-centered design, qualitative methods, and implementation science, and a well-established partnership with the SPH that will ensure an outstanding environment for the proposed research. These studies will determine if oral samples are viable for molecular diagnosis of TB and refine an mHealth strategy for household TB contact tracing, using an innovative design approach that is both theory-informed and community-engaged. This study will ultimately deliver client-centered implementation components for an mHealth contact tracing strategy for future evaluation in a randomized, controlled implementatio...