Fig. 1

Identification of eligible studies on the incidence of active tuberculosis among close contacts. A total of 5,616 articles were obtained by database searches using different combinations of key terms. Among them, 2,653 records excluded because of overlap and 2,552 were excluded by abstracts review due to irrelevant to the study objective. Thus, 411 articles and another 12 cross-references were full text retrieved for more detailed evaluation. Of them, 46 non-original articles and 4 non-English articles were firstly excluded, and then 15 were excluded because the sample size of the studied contacts was less than 100, 238 were excluded because of missing completed incidence-related data, 89 were excluded because did not complete contact tracing, finally, a total of 31 eligible articles were included in this study