RESEARCH ARTICLE A Tuberculin Skin Test Survey and the Annual Risk ofMycobacterium tuberculosis Infection

Background A Tuberculin skin test (TST) survey was conducted to assess the prevalence of latent TB Infection (LTBI) and to estimate the annual risk ofM. tuberculosis infection (ARTI) in Gam-bian school children. The results are expected to contribute to understanding of Tuberculo-sis epidemiology in The Gambia. Methods This was a nationwide, multi-cluster survey in children aged 6–11 years. Districts, 20 of 37, were selected by probability proportional to size and schools by simple random sampling. All TST were performed using the Mantoux method. Height and weight measurements were obtained for all participants. We calculated prevalence of LTBI using cut-off points of 10mm, the mirror and mixture modelling methods. Results TST readings were completed 13,386 children with median age of 9 years (interquartile range [IQR] 8–10 years). Mixture analysis yielded a cut-off point of 12 mm, and LTBI preva