CT FOR EARLY DIAGNOSIS OF SPUTUM-SMEAR NEGATIVE PULMONARY TB IN ENDEMIC POPULATIONS

Abstract

SESSION TITLE: Monday Fellow Case Report Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Early diagnosis of Tuberculosis (TB) is critical for prompt treatment and diagnostic dilemmas can delay appropriate treatment. We review 2 cases of sputum smear-negative pulmonary TB (SSN-pTB). CASE PRESENTATION: Case 1. A 57 year old Chinese man presented with haemoptysis. Radiology revealed a papillary thyroid carcinoma with severe extrinsic tracheal compression and infiltration. He received a total thyroidectomy. Although initial smear and molecular tests were negative on sputum, empiric TB treatment was started given tree-in-bud changes in the right upper lobe on CT. TB cultures from sputum and tracheal aspirates proved TB infection 6 weeks later. Case 2. A 34 year old Filipino pregnant lady presented with haemoptysis and near syncope. Ultrasound of calves were negative for deep venous thrombosis while CT pulmonary angiography revealed only left upper lobe tree in bud changes. Subsequent sputum studies were smear negative but molecular positive TB with culture conversion 2 months later. She was initiated on TB treatment with good outcomes. DISCUSSION: The diagnosis of pTB depends on clinical features and the decision to initiate treatment depends on the pre-test probability. Patients with sputum smear-negative pTB (SSN-pTB) pose as diagnostic dilemmas as they usually have mild symptoms or systemic manifestations. Culture conversion often requires 6-8 weeks to confirm the diagnosis hence losing valuable time for effective and early treatment. Although sputum TB smear and culture are the gold standards in diagnosing pTB, patients may not have sputum. While flexible fiberoptic bronchoscopy can increase the diagnostic yield of SSN-pTB this is invasive and bear risks of complications arising from anticipated difficult airways in both patients. Although empiric TB treatment can be initiated in younger patients with minimal adverse reactions as with the first patient, this cannot be similarly applied to the second patient given clear obstetric and gynaecological considerations to initiating TB treatment without diagnostic confirmation. Confirmation of pTB before initiating treatment is still ideal in either case. CT can be useful in the rapid diagnosis of pTB. Tree-in-bud appearance is the most significant association with active PTB in 24-33% of patients[1] with SSN-pTB. CT features suggestive of pTB reportedly have high sensitivity, specificity as well as positive- and negative- predictive values[2]. In particular, HRCT has been shown to predict the risk of PTB with good reproducibility [3]and is a good diagnostic tool to identify patients with high risk of pTB. CONCLUSIONS: It is important to consider and screen for TB in high risk patients especially if early diagnosis and subsequent treatment of TB is necessary. Tree-in-bud appearance on CT is highly suggestive of PTB in an endemic population and can be useful in the diagnosis of patients with SSN-pTB with difficulty expectorating sputum. Reference #1: Hatipoglu et al . Thorax 1996: 51: 397-402 Reference #2: JS park et al ERJ 2016 48 (60): PA3806 Reference #3: Nakanishi M et al. Eur J Radiol. 2010 Mar;73(3):545-50 DISCLOSURES: no disclosure on file for Kay See; No relevant relationships by Genevieve Tan, source=Web Response