Figure 1a  shows the breakdown of positive and negative Interferon-gamma release assay results against the six reasons described in the following foot notes. Reasons two and four (144/643 and 159/643) show the highest number of negative results. Reason two (111/643) shows the highest number of positive results. The lowest negative result (19/643) was due to reason three. Reason six shows 3 indeterminate results.