A Screening Model for Latent Tuberculosis Infection Among Household Contacts of Patients With Tuberculosis Based on the CyTB Test and an Android App: Protocol for a Development and Implementation Study.

BACKGROUND

Latent tuberculosis infection (LTBI) remains a major barrier to tuberculosis elimination, particularly in community settings where household contacts (HHCs) of patients with active tuberculosis are at increased risk of infection and progression to disease. Current tests for LTBI have practical limitations that restrict their use in field and primary care settings. Antigen-based skin testing, combined with digital tools for induration measurement, may improve the accuracy and delivery of HHC screening under routine program conditions.

OBJECTIVE

This study aims to develop and evaluate a screening model based on CyTB testing and the TBConnect Android app for LTBI among HHCs of patients with confirmed tuberculosis in Rajasthan, India. We will assess its feasibility and operational performance, the prevalence of LTBI among high-risk groups, and implementation outcomes in a routine program setting.

METHODS

This protocol describes a community-based interventional implementation study with a mixed-methods design guided by a logic model and the RE-AIM (reach, effectiveness, adoption, implementation, and maintenance) framework, to be conducted over 24 months in the Balesar block, Jodhpur district, Rajasthan. All eligible HHCs of patients with confirmed tuberculosis identified during the study period will be included, with an estimated screening population of 2400 participants. The intervention combines CyTB-based screening with the TBConnect Android app for participant registration, workflow support, induration recording, follow-up, and reporting. Screening will be implemented through health facility-based, home-based, and camp-based pathways. App-assisted induration measurement will be compared with manual assessment in a subset of participants to evaluate agreement between the 2 methods. Primary outcomes will include screening coverage, LTBI positivity, concordance between app-assisted and manual readings, and feasibility of the 3 screening pathways. Secondary outcomes will include health care worker proficiency, app usability, data completeness, operational efficiency, participant acceptability, and documentation of referral advice among participants with positive CyTB screening results.

RESULTS

Ethical approval was obtained from the institutional ethics committee of ICMR-NIIRNCD (Indian Council of Medical Research-National Institute for Implementation Research on Non-Communicable Diseases), Jodhpur, Rajasthan, India, on August 7, 2025. Recruitment and CyTB screening began in December 2025 and are scheduled to continue until December 2026. Data cleaning and analysis are planned for after field data collection, and the main findings are expected to be submitted for publication in May 2027.

CONCLUSIONS

This protocol describes the implementation and evaluation of a digitally supported CyTB-based LTBI screening model for HHCs of confirmed tuberculosis patients in Rajasthan, India. The study will generate operational evidence on screening coverage, pathway feasibility, agreement between app-assisted and manual induration readings, data completeness, and user acceptability within routine primary health care services.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/95534.