Use of a T-cell interferon-γ release assay for the diagnosis of tuberculous pleurisy

The diagnosis of pleural tuberculosis (plTB) by the analysis of pleural effusions (PEs) with standard diagnostic tools is difficult. In routine clinical practice, the present authors evaluated the performance of a commercially available Mycobacterium tuberculosis (MTB)-specific enzyme-linked immunospot assay on peripheral blood mononuclear cells (PBMCs) and pleural effusion mononuclear cells (PEMCs) in patients with suspect plTB. The T-SPOT.TB test (Oxford Immunotec Ltd, Abingdon, UK) was performed on PBMCs and PEMCs in 20 patients with a clinical and radiological suspect of plTB and in 21 control subjects with a diagnosis of PE of nontuberculous origin at four centres participating in the European Tuberculosis Network. In total, 18 (90%) out of 20 patients with plTB tested T-SPOT.TB-positive on PBMCs and 19 (95%) out of 20 on PEMCs. Among controls, T-SPOT.TB was positive in seven out of 21 (33%) patients when performed on PBMCs (these patients were assumed to be latently infected with MTB) and five (23%) out of 21 when performed on PEMCs. Sensitivity and specificity of T-SPOT.TB for the diagnosis of active plTB when performed on PEMCs were 95 and 76%, respectively. Enumerating Mycobacterium tuberculosis-specific T-cells in pleural effusion mononuclear cells by ELISPOT is feasible in routine clinical practice and may be useful for a rapid and accurate diagnosis of pleural tuberculosis.