The importance of definition of active pulmonary tuberculosis and non-tuberculous pulmonary diseases in studies of diagnostic accuracy in high incidence areas

In a recent study evaluating diagnostic accuracy of the interferon gamma release assay (IGRA) T-SPOT.TB for the diagnosis of tuberculosis in Southern China the authors found a low specificity of this assay in a group of patients with active pulmonary tuberculosis and non-tuberculous pulmonary diseases (NTBPD) (1). The authors may not be right in attributing this entirely to the presence of latent mycobacterium tuberculosis infection in the group of patients with NTBPD.