Assessing an outbreak of tuberculosis in an English college population.

The study population consisted of students enrolled at the college for daytime courses. All participants were aged .16 yrs. Members of staff who directly taught these students were also screened. Between October 2008 and December 2009, students, friends of the index case and staff at the college were interviewed. The interviews were used to collect demographic and clinical information, including symptoms suggestive of tuberculosis. At the same time, a blood sample was drawn from each participant for interferon-c release assay (IGRA) testing [1, 2]. Following the screening of household contacts and friends of the index case, the students at the school were assessed in concentric circles of decreasing intensity of exposure in three groups (table 1) [3]. Those with a positive IGRA result from any screening round were recalled for chest radiography and clinical review at a respiratory medicine clinic. Preventative therapy was offered to all those with no evidence of active tuberculosis and a positive IGRA result who were ,35 yrs of age, according to national guidelines [4]. Detailed results of the IGRA tests are described elsewhere [5].