Diagnostic Usefulness of Bronchoalveolar Lavage Fluid Xpert MTB/RIF in Patients with Suspected Pauci-bacillary Pulmonary Tuberculosis

BACKGROUND: Rapid and accurate diagnosis of tuberculosis (TB) is important for appropriate treatment initiation and control of disease transmission. Xpert TB/RIF has been widely used for rapid diagnosis especially in sputum AFB smear-negative pulmonary TB. However, about one-third of patients with pauci-bacillary pulmonary TB still reveal negative Xpert TB/RIF results from sputum specimens. Theoretically, bronchoalveolar lavage (BAL) fluid can provide more sensitive specimen in those with sputum-scarce or AFB smear-negative pulmonary TB than sputum.However, there is limited data on the diagnostic performance of Xpert TB/RIF from BAL fluid in patients with pauci-bacillary pulmonary TB. METHODS: All patients with suspected pulmonary TB who underwent BAL due to sputum-scarcity or negative AFB smear results and underwent Xpert TB/RIF from BAL fluid were retrospectively reviewed at a tertiary hospital, Seoul, South Korea (an intermediate TB-burden country) between October 2014 and April 2017. Confirmed TB was defined to those with clinical specimens positive for M. tuberculosis by culture or PCR assays. Patients those with caseating granuloma in biopsy tissue and shows a good response to anti-tuberculous therapy were classified as having probable TB. RESULTS: A total of 113 patients were included in the analysis. Of these 113 patients, 30 (27%) were classified as confirmed TB, 7 (6%) as probable TB, and 76 (67%) as not TB. Of these 37 patients with confirmed or probable TB, 8 (22%) had miliary TB and 12 (32%) were immunocompromised. Only 15 (50%) of the 30 confirmed TB patients revealed positive Xpert TB/RIF results from BAL fluid. Overall sensitivity, specificity, positive predictive value, and negative predictive value of Xpert TB/RIF from BAL fluid for the diagnosis of TB were 41% (95% CI, 31%-41%), 100% (95% CI, 95%-100%), 100% (95% CI 77%-100%), and 78% (95% CI 74%-77%), respectively CONCLUSION: XpertTB/RIF from BAL fluid appears to be suboptimal to rule out pulmonary TB. The development of more sensitive and rapid test for pauci-bacillary pulmonary TB is needed. DISCLOSURES: All authors: No reported disclosures.