In this study, clinical concordance between results of the T-SPOT.TB assay, using cells stored for 0-8 hours post venepuncture and isolated via density gradient separation and positive selection with magnetic bead isolation using the T-Cell SelectTM Kit will be assessed. Concordance between results of the T-SPOT.TB assay at 0-8 hours post venepuncture and using cells isolated with density gradient centrifugation and results obtained from cells isolated using the T-Cell Select Kit, following storage between 0-55 hours post venepuncture, will be assessed.