Respiratory Care |

The Accuracy of Xpert MTB/RIF Assay in Bronchoalveolar Specimens and Its Impact on Pulmonary Tuberculosis (PTB) Management FREE TO VIEW

Yingjuan Mok; Thean Yen Tan; Tunn Ren Tay; Hang Siang Wong; Pei Yee Tiew; Jia Wen Kam; Chuin Siau
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Changi General Hospital, Singapore, Singapore

Chest. 2014;146(4_MeetingAbstracts):925A. doi:10.1378/chest.1992976
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SESSION TITLE: Respiratory Infections

SESSION TYPE: Original Investigation Slide

PRESENTED ON: Tuesday, October 28, 2014 at 11:00 AM - 12:15 PM

PURPOSE: Diagnosing pulmonary tuberculosis (PTB) early remains a global challenge. The recent assay, Xpert MTB/RIF, has been a welcoming advance but its utility in bronchoalveolar lavage (BAL) specimens is not well defined. This study aims to assess the accuracy of the Xpert MTB/RIF assay in BAL specimens, its impact on patient treatment, and its potential to challenge the role of transbronchial lung biopsy (TBLB) in increasing diagnostic yields.

METHODS: We identified all patients with no sputum or a negative sputum acid-fast bacilli (AFB) smear, who underwent BAL and TBLB for suspected PTB at our institution between March 2011 and October 2013. A confirmed PTB case was defined by either a positive microbiological culture or completed empirical PTB treatment. We retrospectively reviewed the clinical data, microbiological, histological results and procedural complication rates.

RESULTS: 158 patients were included in our analysis and 54 patients (34.2%) were diagnosed with PTB. We compared the diagnostic yield from the BAL procedure alone (BAL AFB smear and culture+ Xpert MTB/RIF) with that of the combined procedure of BAL and TBLB (BAL AFB smear and culture + TBLB AFB culture and histology) and there was no statistically significant difference. Of the 54 PTB patients, Xpert MTB/RIF diagnosed 30 of the patients (55.6%) soon after bronchoscopy while TBLB histology diagnosed only 8 of them (14.8%) early. The sensitivity and specificity of the Xpert MTB/RIF assay were 55.6% and 98.1% respectively. For the PTB patients, there was a statistically significant difference in the median time to receiving PTB treatment amongst those who had a positive Xpert MTB/RIF result versus those who did not (U = 61.50, p < .001) .The pneumothorax complication rate of TBLB was 6.3%.

CONCLUSIONS: 1.Adding BAL Xpert MTB/RIF to routine BAL analysis produced a diagnostic yield comparable to the combined procedural yield of BAL and TBLB. 2. Xpert MTB/RIF was superior to TBLB histology in the early detection of PTB and expedited the institution of PTB treatment.

CLINICAL IMPLICATIONS: BAL Xpert MTB/RIF has an important role in the early detection and treatment of patients with PTB. It may also obviate the need for TBLB, the latter having a higher pneumothorax risk.

DISCLOSURE: The following authors have nothing to disclose: Yingjuan Mok, Thean Yen Tan, Tunn Ren Tay, Hang Siang Wong, Pei Yee Tiew, Jia Wen Kam, Chuin Siau

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