Xpert MTB/RIF: monitoring response to tuberculosis treatment

TLDR: There has been much interest in whether repeated Xpert MTB/RIF testing during treatment could be used as a marker for response to treatment.

Abstract: Xpert MTB/RIF is an automated nucleic acid amplifi cation test that can be used to simultaneously detect Mycobacterium tuberculosis and identify rifampicin resistance. In 2010, WHO recommended the use of this assay for diagnosis of pulmonary tuberculosis in regions with high rates of HIV and tuberculosis co-infection or multidrug-resistant tuberculosis. 1 In countries where Xpert MTB/RIF testing is now being used, an unresolved question is how to best monitor response to tuberculosis treatment. Failure of the conversion of smear microscopy or culture after 2 months of treatment is used to predict treatment failure or relapse. However, these tests have limitations. 2 Smear microscopy is an insensitive marker of treatment outcome and is of little value when the initial smear is negative. Persistently positive culture at 2 months is common, 3 the assay requires sophisticated infrastructure and highly trained staff , and results are only available after several weeks. Therefore, there has been much interest in whether repeated Xpert MTB/RIF testing during treatment could be used as a marker for response to treatment. In The Lancet Respiratory Medicine, Sven Friedrich and colleagues 4