High diagnostic accuracy of immunodiagnosis in sputum smear/PCR-negative pulmonary tuberculosis

Background: Despite new diagnostic tests early diagnosis of pulmonary tuberculosis (pTB) remains difficult in approximately 15 % of patients who present with negative results of sputum smear microscopy and undetectable M. tuberculosis ( MTB )DNA by PCR. Detection of antigen specific T-cells among BAL cells may provide additional diagnostic information in this situation. Aims and objectives: To ascertain the diagnostic accuracy of a MTB- specific ELISPOT assay with bronchoalveolar lavage mononuclear cells (BALMCs) and peripheral blood mononuclear cells (PBMCs) for the diagnosis of sputum smear microscopy/PCR-negative pulmonary tuberculosis. Methods: In a retrospective case control analysis, patients with MTB culture positive pTB and negative results of sputum smear microscopy/PCR who underwent bronchoscopy for BAL- MTB- specific ELISPOT were matched by age and sex to non-tuberculosis controls with LTBI (positive IGRA result from the blood). ELISPOT results were adjusted to the distribution of lymphocytes and monocytes/macrophages among BALMC and PBMC. Results: Among 13 tuberculosis patients, 12/13 (92%) had a recruitment (BALMC/PBMC) u003e4 adjusted for lymphocytes and 9/13 (69%) adjusted for monocytes/macrophages. Among 13 LTBI patients, 10/13 (77%) had a recruitment Conclusions: Patients with a suspected diagnosis of pulmonary tuberculosis who present with negative results of sputum smear microscopy and undetectable MTB DNA by PCR can still be identified with high sensitivity and specificity by detection of antigen specific T-cells among BAL lymphocytes.