Data are presented as n tests (%) or n tests, where percentages describe the proportion of results returned with that outcome out of the total number of tests performed in that group. ^#: green, amber and red refer to the traffic light categorisation of biologic agents used locally and correspond to increasing risk of tuberculosis re-activation (table 1); ^¶: indeterminate results indicate instances where assay readouts were invalid (e.g. due to a lack of reaction in the control wells), whereas reports categorised as “other” represent tests which were not run (e.g. due to incorrect sampling methods, unacceptable delays in samples reaching the laboratory or laboratory errors). Statistical tests of difference between the outcomes for specific colour groups and the total tests were significant to a level of p<0.05.