585.   Accuracy of  Xpert MTB/RIF for The Diagnosis of Smear-Negative Tuberculosis Using Bronchoalveolar Lavage Fluid in a Hospital Setting
Session: Poster Abstract Session: TB: Mycobacteria Diagnostic Testing
Thursday, October 8, 2015
Room: Poster Hall
Posters
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  • Background: Few studies are available of  accuracy of Xpert MTB/RIF assay  when performed on bronchoalveolar lavage fluid (BALF) obtained from patients with sputum- smear in a hospital setting .Rapid diagnostic test could be useful to implement infection control measures.

    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.

    Fernando Rosso, MD, MSc1, Nora Guarín, MD2, Luisa Martinez, Microbiologist2, Jose Garcia, MD1, Robinson Pacheco, MSC3 and Liliana Fernandez, MD4, (1)Infectious Diseases, Fundación Valle del Lili, Cali, Colombia, (2)Clinical Laboratory, Fundación Valle del Lili, Cali, Colombia, (3)Clinical Research Center, Fundacion Valle del Lili, Cali, Colombia, (4)Pneumology, Fundación Valle del Lili, Cali, Colombia

    Disclosures:

    F. Rosso, None

    N. Guarín, None

    L. Martinez, None

    J. Garcia, None

    R. Pacheco, None

    L. Fernandez, None

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.