Assessment of the Xpert MTB/RIF Ultra assay on rapid diagnosis of extrapulmonary tuberculosis

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ObjectiveTo evaluate the diagnostic performance of Xpert MTB/RIF Ultra for EPTB (Extrapulmonary Tuberculosis) patients on different types of extrapulmonary specimens from different anatomic sites. MethodsPatients with suspected EPTB were prospectively included, extrapulmonary specimens were collected and subjected to culture, Xpert and Xpert Ultra assays in accordance with relevant guidelines. ResultsA total of 225 cases were included which contained 200 EPTB cases (43 culture-positive EPTB, 157 culture-negative EPTB which were diagnosed based on pathological results and a satisfied response to anti-TB treatment) and 25 non-EPTB cases. Sensitivities of Xpert Ultra and Xpert for culture-positive cases were 83.7% (95%CI, 68.7–92.7) and 67.4% (95% CI, 51.3–80.5) respectively. Specificities of Xpert Ultra and Xpert were 92.0% (95% CI, 72.5–98.6) and 96.0% (95% CI, 77.7–99.8) respectively. The sensitivities of Xpert Ultra, Xpert and culture for 200 EPTB cases were 52.5% (105/200, 95% CI, 45.4–59.6), 34.0% (68/200, 95% CI, 27.6–41.1) and 21.5% (43/200, 95% CI, 16.2–28.0) respectively. By comparison among different types of specimens, Xpert Ultra can detect 78.9% (56/71) of EPTB on fine-needle aspiration (FNA) tissues which was higher than that on pleural fluid (43.7% (45/103), p<0.05. ConclusionsXpert Ultra assay had a higher sensitivity than those of Xpert and culture on extrapulmonary specimens, which could be a promising approach for rapid EPTB diagnosis.