Incremental yield of Xpert MTB/RIF Ultra over Xpert MTB/RIF in the diagnosis of extrapulmonary TB.

Extrapulmonary TB (EPTB) comprises approximately 15-20% of TB cases worldwide, and its diagnosis is difficult. The sensitivity of Xpert MTB/RIF (Xpert) in the diagnosis of EPTB is low on account of its paucibacillary nature. Xpert MTB/RIF Ultra (Ultra) was developed to improve sensitivity. To compare the sensitivity of Ultra test with that of Xpert against MGIT™ (Mycobacteria Growth Indicator Tube) culture and a composite reference standard (CRS). We recruited consecutive treatment-naïve patients with suspected EPTB. Demographic information, clinical and relevant laboratory data were collected. From January 2019 to November 2019, 210 patients provided 250 samples. Against MGIT culture, the sensitivity of Ultra was significantly higher than Xpert (72% vs. 51.1%; = 0.04), the specificity was lower (87.8% vs. 95.1%). Against the CRS also, the sensitivity of Ultra was significantly higher than Xpert (45.4% vs. 25.2%; = 0.002); however, the specificities were similar (98.2% vs. 99.1%). The trend towards higher sensitivity of Ultra compared to Xpert was seen in most of the individual samples. The sensitivities against MGIT and CRS were as follows: lymph node (68.1% vs. 31.8%; = 0.01) and (59.5% vs. 23.8%; = 0.001), pleural biopsy (80.0% on both; = NS) and (53.8% vs. 46.2%; = NS) and pleural fluid (66.7% vs. 50%; = NS) and (22.5% vs. 9.6%; = NS), respectively. Xpert Ultra showed a significantly higher sensitivity in diagnosing EPTB than Xpert.