Estimation of annual risk of tuberculosis infection (ARTI) among children aged 1-9 years in the south zone of India.

Kollappan, C.; Gopi, P.G.; Subramani, R.; Chadha, V.K.; Kumar, P.; Venkatesh Prasad, V.; Appegowda, B.N.; Nagabhushana Rao, R.,S.; Sashidharan, R.; Ganesan, N.; Santha, T.; Narayanan, P.R.

International Journal of Tuberculosis and Lung Disease; 2004; 8; 418-423.

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 nation-wide 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 bacilli Calmette-Guerin (BCG) vaccinaton, 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.

Results : Among 52951 children registered for the study, 50 846 (96%) had a tuberculin test result. The BCG coverage for the study population was about 65%. Among 17811 children without a BCG scar, the prevalence of infection was 5.9% (95% CI 4.0-7.7%); the corresponding ARTI was 1.7% (95% CI 0.7-1.4%).

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.

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