ABSTRACT
OBJECTIVE: To estimate the annual risk of tuberculosis infection (ARTI) among children aged 1-9 years in the south zone of India. SETTING: The survey was carried out in a representative sample of villages and census enumeration blocks of towns in four south Indian states, as a part of a nationwide tuberculin survey. DESIGN: Six districts were selected through systematic random sampling. Four hundred and twenty rural clusters and 180 urban clusters were selected from these districts on the basis of the rural-urban ratio in the entire zone. To obtain the required sample of 12,000 children without bacille Calmette-Guérin (BCG) vaccination, 51,000 had to be covered. Eighty-five children from each cluster were tuberculin tested and read for reaction sizes. The ARTI was computed from the estimated prevalence of TB infection among children without a BCG scar. RESULT: Among 52,951 children registered for the study, 50,846 (96%) had a tuberculin test result. The BCG coverage for the study population was about 65%. Among 17,811 children without a BCG scar, the prevalence of infection was 5.9% (95%CI 4.0-7.7%); the corresponding ARTI was 1.0% (95%CI 0.7-1.4%) [correction]. CONCLUSION: The estimated ARTI for the south zone is 1.0%, as compared to the national average of 1.7% used for programme evaluation. This baseline information should be useful for the assessment of future trends.
