High risk of tuberculous infection in North Sulawesi Province of Indonesia.

Setting: Of all the provinces in Indonesia, the highest tuberculosis (TB) case notification rates are reported from North Sulawesi Province.

Objective: To estimate the annual risk of tuberculous infection (ARTI) among schoolchildren in the 6-9 year age group.

Methods: A cross-sectional survey was carried out in 99 schools selected by a two-stage sampling process. Children attending grades 1-4 in the selected schools were administered intradermally with 2 tuberculin units (TUs) of purified protein derivative RT23 with Tween 80, and the maximum transverse diameter of induration was measured about 72 h later. A total of 6557 children in the 6-9 year age group were satisfactorily test-read, irrespective of their bacille Calmette-Guérin (BCG) vaccination status.

Results: Based on the frequency distribution of reaction sizes obtained among satisfactorily test-read children (without and with BCG scar), the estimated ARTI rates when estimated by different methods (anti-mode, mirror-image and mixture model) varied between 1.9% and 2.5%. BCG-induced tuberculin sensitivity was not found to influence the ARTI estimates, as the differences in estimates between children without and with BCG scar were not statistically significant.

Conclusion: TB control efforts should be further intensified to reduce the risk of tuberculous infection.