The diagnostic accuracy of the GenoType® MTBDRsl assay for the detection of resistance to second-line anti-tuberculosis drugs

Abstract

Different drugs are available to treat people with tuberculosis (TB), but resistance to these drugs is a growing problem. People with drug-resistant TB are more likely to die than people with drug-susceptible TB. People with drug-resistant TB require \"second-line\" TB drugs that, compared with \"first-line\" TB drugs used to treat drug-susceptible TB, cause more side effects and must be taken for longer. Extensively drug-resistant TB (XDR-TB) is a type of TB that is resistant to almost all TB drugs. A rapid and accurate test could identify people with drug-resistant TB, likely improve patient care, and reduce the spread of drug-resistant TB.

GenoType® MTBDRsl (MTBDRsl) is the only rapid test that detects resistance to second-line fluoroquinolone drugs and the second-line injectable drugs. The test also detects XDR-TB. MTBDRsl can be performed on TB bacteria grown by culture from sputum, which takes a long time (indirect testing), or immediately on sputum (direct testing).

We examined evidence available up to 30 January 2014 and included 21 studies, 11 of which were in low-income or middle-income countries.

By indirect testing, the test detected 83% of people with fluoroquinolone resistance and rarely gave a positive result for people without resistance. In a population of 1000 people, where 170 have fluoroquinolone resistance, MTBDRsl will correctly identify 141 people with fluoroquinolone resistance and miss 29 people. In this same population of 1000 people, where 830 people do not have fluoroquinolone resistance, the test will correctly classify 811 people as not having fluoroquinolone resistance and misclassify 19 people as having resistance (moderate quality evidence).

By direct testing, the test detected 85% of people with fluoroquinolone resistance and rarely gave a positive result for people without resistance (moderate quality evidence).

By indirect testing, the test detected 77% of people with second-line injectable drug resistance and rarely gave a positive result for people without resistance. In a population of 1000 people, where 230 have second-line injectable drug resistance, MTBDRsl will correctly identify 177 people with second-line injectable drug resistance and miss 53 people. In this same population of 1000 people, where 770 do not have second-line injectable drug resistance, the test will correctly classify 766 people as not having second-line injectable drug resistance and misclassify four people as having resistance (moderate quality evidence).

By direct testing, the test detected 94% of people with second-line injectable drug resistance and rarely gave a positive result for people without resistance (very low quality evidence).

By indirect testing, the test detected 71% of people with XDR-TB and rarely gave a positive result for people without XDR-TB. In a population of 1000 people, where 80 have XDR-TB, MTBDRsl will correctly identify 57 people with XDR-TB and miss 23 people. In this same population of 1000 people, where 920 do not have XDR-TB, the test will correctly classify 909 people as not having XDR-TB and misclassify 11 people as having XDR-TB (low quality evidence).

There was insufficient evidence to determine the accuracy of MTBDRsl by direct testing for XDR-TB.

The results show that a positive MTBDRsl result for resistance to the fluoroquinolone drugs or the second-line injectable drugs is reliable evidence that the person has drug-resistant TB and further conventional drug-resistance testing is not required. However, when the test reports a negative result, clinicians may still wish to carry out conventional testing.

Citation

Theron, G.; Peter, J.; Richardson, M.; Barnard, M.; Donegan, S.; Warren, R.; Steingart, K.R.; Dheda, K. The diagnostic accuracy of the GenoType® MTBDRsl assay for the detection of resistance to second-line anti-tuberculosis drugs. Cochrane Database of Systematic Reviews (2014) Issue 10, Art. No.: CD010705. [DOI: 10.1002/14651858.CD010705.pub2]

The diagnostic accuracy of the GenoType® MTBDRsl assay for the detection of resistance to second-line anti-tuberculosis drugs

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