Diagnostic accuracy of TB PCR in mediastinal lymph node TB in a UK centre using EBUS-TBNA

<b>Introduction:</b> Xpert Ultra has a higher diagnostic sensitivity compared to Xpert MTB/RIF in sputum and its role in EBUS-TBNA is still unclear. <b>Aims:</b> To compare the diagnostic accuracy of Xpert Ultra for the detection of MTB in mediastinal lymph nodes using EBUS-TBNA against conventional modalities (microscopy, culture, cytology) and a clinical composite diagnosis. <b>Methods:</b> A retrospective observational study analysing EBUS-TBNA samples from January 2018 to June 2019 was performed. Patient demographics, phenotypes and results were recorded using patient records and the London TB Registry. <b>Results:</b> A total of 156 EBUS-TBNA samples were analysed with a median age of 54 (IQR 41-65.25), M:F ratio of 94:62, 7 patients with previous TB and 4 patients with HIV. A total of 18 were culture positive with a median time to culture positivity of 16.5 days (IQR 15-19.5), with a mean of 6 passes taken from any lymph node. Of the culture positive cases, 11 were Xpert Ultra positive and 2 were trace results. 3 trace results were culture negative in previously never treated cases. All patients with trace results were immunosuppressed (diabetes, renal failure or on steroids). Xpert Ultra results were available on the same day except in 2 cases. The diagnostic accuracy tests are summarised in Figure 1: <b>Conclusion:</b> Xpert Ultra offers a rapid point-of-care diagnostic test in EBUS-TBNA samples with a greater sensitivity over smear in mediastinal TB.