Characteristics of the 8/73 (11%) interpretable T-SPOT®.TB assays.

*As per the manufacturer's guidelines, an assay was considered valid if the number of SFU's/106cells in the negative control well was twice that of the positive control well. A value of >250SFU's/106cells was selected as the cut-off positive value. ESAT-6 = Early Secretory Antigen Target-6. CFP-10 = Culture Filtrate Protein-10. SI = Induced sputum sample.#Insufficient cells to plate both wells.+Patients were found to be culture positive on other biological samples and therefore classified as definite TB.$Asymptomatic control patient with COPD and normal chest x-ray (sputum smear and culture was not indicate.