Redefining MTBDRplus test results: what do indeterminate results actually mean?

Nikam, C. and Patel, R. and Sadani, M. and Ajbani, K. and Kazi, M. and Soman, R. and Shetty, A. and Georghiou, S. B. and Rodwell, T. C. and Catanzaro, A. and Rodrigues, C. (2016) Redefining MTBDRplus test results: what do indeterminate results actually mean? Int J Tuberc Lung Dis, 20 (2). pp. 154-159.

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BACKGROUND: Although line-probe assays (LPAs) are promising, little research has been conducted to elucidate the true nature of indeterminate LPA results or assess the ability of these assays to perform on a wide range of clinical samples. OBJECTIVE: To evaluate the performance of the commercially available GenoType(®) MTBDRplus LPA against conventional BACTEC™ MGIT™ 960 culture and drug susceptibility testing (DST) among 308 pulmonary tuberculosis (PTB) and 32 extra-pulmonary TB samples. RESULTS: Invalid LPA results (defined as those with a missing Mycobacterium tuberculosis identification band) were obtained for 18 PTB samples, which were excluded from further analysis. The sensitivity and specificity of the MTBDRplus assay for multidrug-resistant TB, based upon the results obtained for the remaining 322 samples, was respectively 95.2% and 95.1%. Of 290 PTB samples, 40 (13.7%) were indeterminate on LPA (defined as the absence of both wild-type and corresponding mutation bands) for isoniazid (INH) and/or rifampicin (RMP), and were further evaluated by pyrosequencing (PSQ). Contrary to standard LPA interpretation, INH and RMP susceptibility were confirmed by both DST and PSQ in respectively 7.5% (3/40) and 27.5% (11/40) of indeterminate samples. CONCLUSION: PSQ was found to be a valuable and rapid technique to resolve discrepancies in LPA test results that were not interpretable.

Item Type: Article
Uncontrolled Keywords: Tuberculosis; Drug resistance; Pyrosequencing; Heteroresistance; Indeterminate
Subjects: Tuberculosis > Drug Resistant TB
Institutions: National Task Force, Zonal Task Force & State Task Force of Medical Colleges
Depositing User: Mr SANJAY SINGH
Date Deposited: 29 Jan 2016 09:46
Last Modified: 29 Jan 2016 09:46

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