TB OR NOT TB?

Abstract

SESSION TITLE: Monday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Testing for active pulmonary TB is often triggered by symptoms such as fever, cough, night sweats. We present an atypical case of pulmonary TB. CASE PRESENTATION: A 69-year-old Filipino man presented to ED for psychiatric clearance due to report of domestic violence. Initial work-up was only remarkable for chest XR finding of bilateral upper lobe infiltrates. Quantiferon was negative. Patient denies any cough, fever, night sweat, or weight loss. He had moved from the Philippines over 40 years ago, but had no recent foreign travels or known TB exposures. However, given chest XR finding, airborne isolation and TB rule-out testing with MTB-PCR and sputum cultures were pursued. CT chest showed bilateral upper lobe cavitary nodules. As patient could not produce sputum samples, he underwent bronchoscopy. Result of MTB-PCR was positive. Bronchial washing culture later was also positive for MTB, which confirmed the diagnosis of active pulmonary TB. DISCUSSION: Current diagnostic approach to pulmonary TB involves an initial clinical suspicion followed by chest imaging and if indicated, testing with MTB-PCR or sputum culture. However, in our case, the patient presented with a completely different chief complaint, and did not have any history or physical exam findings suggestive of TB. Had a chest X-ray not been done, the incidental finding of bilateral upper lobes infiltrates would not have been found, work-up for TB would not have been pursued, and his active pulmonary TB would not have been discovered. Also interestingly, his Quantiferon was negative, although final confirmatory TB testing was positive. Upon literature search, case report of subclinical active pulmonary TB in immunocompetent adults is rare. One population-based study in China in 2015 did find a high percentage of asymptomatic pulmonary TB patients, and called into question the conventional criteria for initiating TB testing. However, there was no follow-up study performed according to the best of our knowledge. Our patient similarly reminds us that subclinical pulmonary TB may not be uncommon as presumed. In addition, based on a study done in Europe in 2011, Quantiferon, which tests for interferon-gamma response to TB antigens, has a sensitivity of only 80% for active TB. Therefore, Quantiferon should not be used as a rule out test for active TB. Also of note, old age is a recognized risk factor for false negative Quantiferon, as the interferon-gamma response to TB antigenic targets decreases with age. CONCLUSIONS: Active pulmonary TB can present subclinically. Delay in treatment in these patients, due to our current symptoms-based trigger for TB testing, can have widespread effect on patient outcome and epidemiological consequences. Further re-examination of our diagnostic approach to active TB testing should be pursued. It is also important to remember that a negative Quantiferon test does not rule out active pulmonary TB Reference #1: M. Sester, et al. Interferon-γ release assays for the diagnosis of active tuberculosis: a systematic review and meta-analysis. European Respiratory Journal Jan 2011 Reference #2: Cheng J, Wang L, Zhang H, Xia Y. Diagnostic value of symptom screening for pulmonary tuberculosis in China. Reference #3: Veerle de Visser, et al. False-negative interferon-γ release assay results in active tuberculosis: a TBNET study. European Respiratory Journal Jan 2015 DISCLOSURES: No relevant relationships by Chia-Dan Kang, source=Web Response No relevant relationships by Arhama Malik, source=Web Response