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Int J Tuberc Lung Dis. 2011 Jul;15(7):959-65. doi: 10.5588/ijtld.10.0515.

Evaluation of the Genotype® MTBDRplus assay as a tool for drug resistance surveys.

Author information

1
Microbiology Department, Institute of Tropical Medicine, Antwerp, Belgium. lrigouts@itg.be

Abstract

SETTING:

A national tuberculosis (TB) drug resistance survey in Tanzania.

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.

PMID:
21682972
DOI:
10.5588/ijtld.10.0515
[Indexed for MEDLINE]

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