First national tuberculin survey in Nepal

Abstract

Setting: The size of the tuberculosis (TB) problem in Nepal is unknown, as no national tuberculin or TB prevalence survey has yet been performed.

Objective: To assess the prevalence of TB infection and the annual risk of TB infection (ARTI) in primary schoolchildren in the three ecological zones (mountains, hills and terai) and Kathmandu valley.

Design: A representative sample of primary schoolchildren were tuberculin skin tested using the Mantoux method. The data were analysed using cut-off levels to define infection and by the mirror method.

Results: Of 19577 children registered, 17260 (88.2%) were available for analysis. Seventy-eight per cent had a visible bacille Calmette-Guérin scar. The best estimate of the prevalence of TB infection was 7.0% (95%CI 4.2-9.7), with an ARTI of 0.86% (95%CI 0.49-1.23) using the mirror method, with a mode at 16 mm. Although the ARTI was higher in Kathmandu and the mountains compared to the hills and terai, the difference between the areas was not significant.

Conclusion: The ARTI in Nepal is lower than previous estimates, indicating a decrease in transmission or overestimation of previous estimates. To obtain information about the trend of the ARTI in Nepal, the survey needs to be repeated in 5 to 7 years.