Methods: Retrospective cohort study. Patients with pulmonary infiltrates who underwent bronchoscopy and who were sputum- smear-negative were included Xpert MTB/RIF was performed on a resuspended pellet of centrifuged BALF.
Results: Between august 2011 and july 2013, 767 samples were tested. From these, 28 (3.6 %) were positive . From those initial positive samples, mycobacteria culture was positive in 11 (39.2%) . Of those who had negative cultures, all the Xpert detection was detected as low or very low. From those who had negative Xpert , 739 (96.3%) only 5 had positive culture fro MTB (0.7%) . With a prevalence of 2.09% ,the overall sensitivity was 68,7%, specificity 97.7% , Positive predictive value 39,3%, and negative predictive value 99,3%.
Conclusion: Our study found a low MTB infection (2%) in these smear negative samples. The low positive predictive value can be explained because of these low prevalence, although Xpert MTB had a very high specificity and negative predictive value. A negative Xpert in a negative smear sample of BALF could rule out pulmonary TB.
L. Martinez, None
J. Garcia, None
R. Pacheco, None
L. Fernandez, None