Rapid tests for multidrug resistant tuberculosis in low income settings

<p>Tuberculosis (TB) is at epidemic levels in the resource-limited settings (RLSs) due to HIV/AIDS, poverty and insufficient TB control programmes. These factors are also contributing to TB drug resistance. Patients with multidrug drug resistant tuberculosis (MDR-TB) do not respond to first line drugs. These patients require unique drug regimens, making it necessary to routinely screen for MDR-TB. Screening for MDR-TB with the Lowenstein-Jensen proportion method (LJPM), which is common in the RLSs is a very slow process taking 2-3 months. More rapid tests suitable for RLSs are urgently needed. In this thesis, a comparison of the technical and operational performance of several rapid tests for MDR-TB was done, and the most optimal tests for RLSs are proposed.</p><p>In paper I, a meta-analysis of rapid tests for direct detection of MDR-TB was conducted. The direct nitrate reductase assay (NRA), microscopic observation drug susceptibility (MODS) and Genotype® MTBDRplus (GT-DRplus) were highly sensitive and specific, and far more rapid than the conventional indirect drug susceptibility testing (DST).</p><p>In paper II, the NRA, MODS, Mycobacterium Growth Indicator Tube (MGIT 960), GT-DRplus, Alamar blue, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and resazurin assays were compared head-to-head for indirect detection of MDR-TB at the National Tuberculosis Reference Laboratory (NTRL) Kampala. The NRA, MGIT 960, GT-DRplus and MODS were the most sensitive and specific tests, with significantly shorter time to results compared to the LJPM.</p><p>In paper III, the direct NRA and MODS assays were compared at the NTRL on sputum specimens from consecutive re-treatment TB patients. Interpretable results were obtained in over 90% of the samples with both assays. The median days to results were 10 with the NRA and 7 with MODS. The direct NRA was more sensitive and specific, and was cheaper.</p><p>In paper IV, the sensitivity, specificity, time to results (TTR) and reproducibility of the direct GTDRplus against the MGIT 960 was assessed. Sensitivity and specificity were 100% and 96% for detection of rifampicin resistance; 81%, and 100% for isoniazid resistance; and 92%, and 96%, for MDR-TB, respectively. The TTR was 1-3 days, and concordance of results between the Molecular Laboratory at Makerere University and the FIND Diagnostics Laboratory was 98%.</p><p>In paper V, we applied spoligotyping to study the clustering rate and predominant genotypic strains of 99 MDR-TB strains isolated from patients in Kampala. Eighty-three percent of the strains occurred in clusters, and the T2 lineage was the largest single cluster.</p><p>Conclusion. The direct NRA and the GT-DRplus appear to be the most appropriate tests for MDR-TB in RLSs. The NRA being the cheapest test can be applied where resources are extremely limited, while the ultra rapid but commercially available GT-DRplus can be used where resources permit.</p><h3>List of scientific papers</h3><p>I. Bwanga F, Hoffner S, Haile M, Joloba ML. (2009). "Direct susceptibility testing for multi drug resistant tuberculosis: a meta-analysis" BMC Infect Dis 9: 67 <br><a href="https://pubmed.ncbi.nlm.nih.gov/19457256">https://pubmed.ncbi.nlm.nih.gov/19457256</a><br><br></p><p>II. Bwanga F, Joloba ML, Haile M, Hoffner S. (2010). "Evaluation of seven tests for the rapid detection of multidrug-resistant tuberculosis in Uganda." Int J Tuberc Lung Dis 14: 890-895 <br><a href="https://pubmed.ncbi.nlm.nih.gov/20550774">https://pubmed.ncbi.nlm.nih.gov/20550774</a><br><br></p><p>III. Bwanga Freddie, Melles Haile, Sven Hoffner, Emmanuel Ochom, Moses L. Joloba. (2010). "Direct Nitrate Reductase Assay versus Microscopic Observation Drug Susceptibility for rapid detection of MDR-TB in Uganda." (Manuscript)</p><p>IV. Albert H, Bwanga F, Mukkada S, Nyesiga B, Ademun JP, Lukyamuzi G, Haile M, Hoffner S, Joloba M, OBrien R. (2010). "Rapid screening of MDR-TB using molecular Line Probe Assay is feasible in Uganda." BMC Infect Dis 10: 41 <br><a href="https://pubmed.ncbi.nlm.nih.gov/20187922">https://pubmed.ncbi.nlm.nih.gov/20187922</a><br><br></p><p>V. Bwanga Freddie, William George Muyombya, Sven Hoffner, Melles Haile, Benon Asiimwe, David Kateete, Fred Katabazi, Jennifer Asiimwe, Maria Wijkander, Moses L Joloba. (2010). "High clustering of MDR-TB strains in Kampala, Uganda: Predominance of the T2 lineage." (Manuscript)</p>