Rapid diagnosis of pulmonary tuberculosis by combined molecular and immunological methods

Abstract

Diagnosing pulmonary tuberculosis (TB) may be delayed until culture results become available.We ascertained the accuracy of a stepwise diagnostic algorithm for the rapid diagnosis of pulmonary TB by GeneXpert from sputum and/or bronchoalveolar lavage (BAL) followed by a <i>Mycobacterium tuberculosis-</i>specific BAL ELISPOT assay in patients with a suspected diagnosis of pulmonary TB at a clinical referral centre in Germany.Among 166 patients with a presumptive diagnosis of pulmonary TB, 81 cases were confirmed by <i>M. tuberculosis</i> culture from sputum and/or BAL. In 66 out of 81 (81.5%) cases, patients initially had <i>M. tuberculosis</i> detected by GeneXpert from sputum; in addition, six out of 81 (7.4%) cases were diagnosed by GeneXpert on BAL fluid (together 72 out of 81 (88.9%) patients). Out of the remaining nine patients with negative GeneXpert results from sputum and BAL, BAL ELISPOT identified eight patients with culture-confirmed TB correctly (median time to culture positivity 26 days). At a cut-off of >4000 early secretory antigenic target-6- or culture filtrate protein-10-specific interferon-γ-producing lymphocytes per 1 000 0000 lymphocytes, the specificity of the BAL ELISPOT for active TB was 97%.In low TB incidence countries, nearly all patients with active pulmonary TB can be identified within the first few days of clinical presentation using a stepwise strategy with GeneXpert and BAL ELISPOT.