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

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 av...

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Veröffentlicht in:The international journal of tuberculosis and lung disease 2016-02, Vol.20 (2), p.154-159
Hauptverfasser: Nikam, C., Patel, R., Sadani, M., Ajbani, K., Kazi, M., Soman, R., Shetty, A., Georghiou, S. B., Rodwell, T. C., Catanzaro, A., Rodrigues, C.
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Sprache:eng
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Zusammenfassung: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.
ISSN:1027-3719
1815-7920
DOI:10.5588/ijtld.15.0319