Household contact investigation for tuberculosis in Vietnam: study protocol for a cluster randomized controlled trial

BACKGROUND: Tuberculosis is an infectious disease that continues to cause considerable morbidity and mortality globally. Only 65% of patients worldwide are currently diagnosed. Contact investigation is a strategy that aims to increase case detection and reduce transmission of tuberculosis, yet there is little evidence to show its effectiveness. METHODS/DESIGN: We will conduct a cluster randomized controlled trial of contact investigation within the national tuberculosis control program of Vietnam. Household contacts of patients with smear-positive pulmonary tuberculosis will be invited to attend district tuberculosis units for symptom screening, examination, and chest radiography on four occasions over a two-year period. The primary endpoint is clinically confirmed tuberculosis among contacts during the 24 months of follow-up, ascertained using capture-recapture analysis. Microbiologically proven tuberculosis and treatment completion rates among contacts diagnosed with tuberculosis will be secondary endpoints. The incremental cost-effectiveness ratio will be estimated. The study will have 80% power to detect a 50% increase in the primary endpoint in the active intervention arm compared with the control arm. The study will include 8,829 contacts in each of the active screening and control groups, within 70 districts in 8 provinces in Vietnam, in both rural and urban settings. DISCUSSION: The effectiveness of contact investigation as a tool for improved tuberculosis case finding has not been established. This cluster randomized trial will provide valuable operational information for national tuberculosis programs in high-prevalence countries, in order to select the most cost-effective strategies to improve tuberculosis case detection. TRIAL REGISTRATION: The ACT2 study has been registered with the Australian New Zealand Clinical Trials Registry (ACTRN12610000600044).