A 4 ml blood sample was obtained from each participant in an EDTA blood collection tube for subsequent plasma separation. Three additional aliquots were obtained at the same time for the QuantiFERONH-TB Gold in tube assay. Plasma was obtained before initiating TB treatment; otherwise plasma was taken within 1-2 days of treatment. Blood samples were transferred to the central laboratory on ice. Plasma was separated (3500 rpm, 10 minutes), aliquoted and frozen at 270uC at 6 hours following collection.