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

Abstract

BACKGROUND: 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.OBJECTIVE: To compare the sensitivity of Ultra test with that of Xpert against MGIT™ (Mycobacteria Growth Indicator Tube) culture and a composite reference standard (CRS).METHODS: We recruited consecutive treatment-naïve patients with suspected EPTB. Demographic information, clinical and relevant laboratory data were collected.RESULTS: 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%; P = 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%; P = 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%; P = 0.01) and (59.5% vs. 23.8%; P = 0.001), pleural biopsy (80.0% on both; P = NS) and (53.8% vs. 46.2%; P = NS) and pleural fluid (66.7% vs. 50%; P = NS) and (22.5% vs. 9.6%; P = NS), respectively.CONCLUSIONS: Xpert Ultra showed a significantly higher sensitivity in diagnosing EPTB than Xpert.

The diagnostic performance of endobronchial ultrasound with Xpert MTB/RIF Ultra in smear-negative pulmonary tuberculosis

“…Ultra has already been applied to diagnose extrapulmonary tuberculosis. In the diagnosis of pleural TB, Ultra using pleural fluids is better than Xpert [ 20 , 21 ], but using biopsy samples maybe even better [ 22 – 24 ]. One study combining pathological examination for biopsy with Ultra increased the sensitivity to 92.59% (25/27) [ 25 ].…”

“…One study combining pathological examination for biopsy with Ultra increased the sensitivity to 92.59% (25/27) [ 25 ]. It is the same on other types of tissue samples, like lymph node aspirate or lymph node biopsy [ 21 , 26 ] and bone or joint aspirate [ 27 , 28 ]. However, the increased sensitivity of Ultra reduces the overall specificity in high-burden TB settings for detecting of dead bacilli in patients with recent history of TB [ 3 ].…”

Combined plasma cell-free DNA detection and IFN-γ/TNF-α dual fluorospot assays for diagnosing active tuberculosis

“…According to recent studies, the sensitivities of Xpert MTB/RIF Ultra for pulmonary and smear-positive TB are high, 90% or more, but low, between 45% and 78.6%, for extra-pulmonary and smear-negative TB [2,13,14]. In the present study, the sensitivity of the combined cfDNA and IFN-γ/TNF-α dual release assays for 32 patients with extra-pulmonary TB and disseminated TB (Supplemental Table 3) was 90.6% (29/32), which was comparable to the sensitivity for pulmonary TB (90.9%, 20/22) (Supplemental Table 2).…”

Pleural effusion guidelines from ICS and NCCP Section 1: Basic principles, laboratory tests and pleural procedures

“…The diagnostic yield of MT reaches close to 100% for tubercular aetiology when histopathology and mycobacterial cultures and GeneXpert are performed on thoracoscopic samples. [ 95 96 ] MT also offers a high diagnostic yield for malignancy, providing adequate tissue samples for immunohistochemistry (IHC) studies in addition to histopathology. It also has the added advantage of being able to perform pleurodesis in the same sitting.…”