Evaluation of the Genotype® MTBDRplus assay as a tool for drug resistance surveys
OBJECTIVE: To compare the performance of the Genotype® MTBDRplus line-probe assay (LPA) on smear-positive sputum specimens with conventional culture and isoniazid (INH) plus rifampicin (RMP) drug susceptibility testing (DST).
DESIGN: Mycobacterium tuberculosis isolates tested at the Tanzanian Central TB Reference Laboratory (CTRL) were submitted for quality assurance of phenotypic DST to its supranational reference laboratory (SRL), together with ethanol-preserved sputum specimens for LPA DST.
RESULTS: Only 321 samples could be tested using LPA; of these, three were identified as being non-tuberculous mycobacteria using CTRL DST. Both tests had 269 sets with interpretable results. CTRL DST yielded almost the same number of interpretable results as LPA, with 90% concordance (κ = 0.612, P < 0.001). Five (1.9%) multidrug-resistant (MDR) strains, 46 (17.1%) resistant to INH only and 0 RMP only, were found by CTRL DST. For the LPA, these results were respectively 5 (1.9%), 26 (9.7%) and 2 (0.7%). With SRL DST as the gold standard, LPA was more accurate than CTRL DST for RMP, but missed almost half the INH-resistant samples.
CONCLUSION: LPA applied directly on ethanol-preserved sputum specimens was similar to phenotypic DST in terms of yield of interpretable results. Although probably more accurate for RMP and MDR-TB, it appears to seriously underestimate INH resistance. Considering speed, easy and safe specimen transportation and low infrastructure requirements, LPA DST from sputum can be recommended for surveys in resource-poor settings.
Document Type: Regular Paper
Affiliations: 1: Microbiology Department, Institute of Tropical Medicine, Antwerp, Belgium; Department of Pharmacy, Veterinary and Biomedical Sciences, University of Antwerp, Antwerp, Belgium 2: Microbiology Department, Institute of Tropical Medicine, Antwerp, Belgium 3: Central Tuberculosis Reference Laboratory, Dar Es Salaam, Tanzania 4: World Health Organization, Geneva, Switzerland 5: KNCV Tuberculosis Foundation, The Hague, The Netherlands; Center for Poverty-Related Communicable Diseases, Amsterdam Institute for Global Health and Development, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands 6: National Tuberculosis and Leprosy Control Programme, Ministry of Health and Social Welfare, Dar es Salaam, Tanzania 7: Microbiology Department, Institute of Tropical Medicine, Antwerp, Belgium; International Union Against Tuberculosis and Lung Disease, Paris, France
Publication date: 2011-07-01
The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.
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