151 patients with active TB and 110 symptomatic controls were recruited (Figure 1 ). Of patients with active TB, 139 were both smear and culture positive, with the remainder either smear or culture positive. 48% of symptomatic controls had LTBI on the basis of a positive QuantiferonGold assay. Symptomatic controls had clinical features overlapping those of active TB patients, including cough, haemoptysis, fever, night sweats and weight loss, although symptom duration was generally longer among TB patients. Similar proportions of TB patients and symptomatic controls reported a previous history of TB (22% vs. 18%). The proportion reporting a history of TB was higher among controls with LTBI than among those without but did not reach statistical significance. Patients with active TB had lower BMIs at the time of recruitment compared with symptomatic controls (21.6 vs. 24.1 p,0.001). As expected, a higher proportion of patients with LTBI based on a positive IGRA had positive TSTs (.10 mm) compared with those without LTBI (62% vs. 30%, p,0.001). There was a higher proportion of female patients among the symptomatic controls than among the TB group. The effects of this potential bias are discussed below. Other key clinical features of the participant groups are given in Table 1 .