Evaluation of Xpert MTB/XDR test for susceptibility testing of Mycobacterium tuberculosis to first and second-line drugs in Uganda

Abstract

Background Drug-Resistant Tuberculosis (DR-TB) is one of the major challenges to TB control. Design and methods This was a blinded, laboratory-based cross-sectional study using sputum samples or culture isolates. Samples were from patients with rifampicin-resistant—TB and/or with high risk for isoniazid (INH) resistance and/or 2nd line fluoroquinolones (FQ) and injectable agents (IAs). The diagnostic accuracy of the Xpert® MTB/XDR test was compared to MGIT960 and the Hain Genotype® MTBDRplus and MDRsl assays (LPA) as reference DST methods. Factors for laboratory uptake of the Xpert® MTB/XDR test were also evaluated. Results Of the 100 stored sputum samples included in this study, 65/99 (65.6%) were resistant to INH, 5/100 (5.0%) were resistant to FQ and none were resistant to IAs using MGIT960. The sensitivity and specificity, n (%; 95% Confidence Interval, CI) of Xpert® MTB/XDR test for; INH was 58 (89.2; 79.1–95.5) and 30 (88.2; 72.5–96.6) and for FQ; 4 (80.0; 28.3–99.4) and 95 (100; 96.2–100), respectively. Using LPA as a reference standard, a total of 52/98 (53.1%) were resistant to INH, 3/100 (3.0%) to FQ, and none to IA. The sensitivity and specificity, n (%; 95%CI) of Xpert® MTB/XDR test compared to LPA for; INH was 50 (96.1; 86.7–99.5) and 34 (74.0; 58.8–85.7) for FQ 3 (100; 29.2–100) and 96 (99.0; 94.3–99.9) respectively. The factors for laboratory uptake and roll-out of the Xpert® MTB/XDR test included: no training needed for technicians with, and one day for those without, previous Xpert-ultra experience, recording and reporting needs were not different from those of Xpert-ultra, the error rate was 4/100 (4%), one (1%) indeterminate rate and test turn-around-time were 1hr/45 minutes. Conclusion There is high sensitivity and specificity of Xpert® MTB/XDR test for isoniazid and fluoroquinolones. There are acceptable Xpert® MTB/XDR test attributes for the test uptake and roll-out.

Predisposing, enabling, and need factors influencing rapid uptake of the World Health Organization-endorsed TB diagnostic technologies in Africa

“…This quick uptake, a few years after its recommendation (2 years) could be linked to the fact that no additional training was needed for technicians who had previous experience using Xpert Ultra or a minimum training, of at least one day was needed for those without previous experience with. Our findings are in line with those reported recently by Katamba et al 18…”

“…This quick uptake, a few years after its recommendation (2 years) could be linked to the fact that no additional training was needed for technicians who had previous experience using Xpert Ultra or a minimum training, of at least one day was needed for those without previous experience with. Our findings are in line with those reported recently by Katamba et al 18 As a funder of the NTRL and driver of the implementation, the Ministry of Health is ranked highest for both, with 18 (38%) and 27 (57%) respondents respectively. On average, 35% of respondents found that funding for the NTRL is from domestic and the driver of the TB diagnostics implementation is national for 52% of respondents.…”

“…In contrast to the Xpert MTB/RIF and Ultra, the test can only run on a 10-color machine, hence the swap from 6-color by the manufacturer should be encouraged. 18 The running cost, the infrastructure, equipment maintenance, and skilled personnel are the most noted limitations for the optimal utilization of Xpert in general.…”

Rapid Diagnosis of Drug-Resistant Tuberculosis–Opportunities and Challenges

“…In people with known rifampicin resistance, Xpert MTB/XDR sensitivity and specificity for ETH resistance were 98% and 99.7% respectively. For amikacin resistance, the Xpert MTB/XDR sensitivity and specificity were 86% and 99% [88]. This assay is recommended as a reflex text in people diagnosed with rifampicin-resistant tuberculosis in countries with a high burden of DR-TB.…”