Les encouragements sont nombreux pour une mise en place rapide et étendue du nouveau test diagnostique de la TB Xpert ® MTB/RIF. Dans le numéro de décembre de l'International Journal of Tuberculosis and Lung Disease (IJTLD), les experts de L'Union en matière de tuberculose donnent leur avis sur le sujet.

"Xpert® MTB/RIF for NTPs in low-income countries: when, where and how?" states that this test offers new and important possibilities for the diagnosis of sputum smear-negative tuberculosis (TB) and/or rifampicin (RMP) resistance. It points out, however, that in low-income countries (LICs), its cost; environmental limitations, such as stable and regular electricity and adequate room temperature; and difficulties involved in supply and maintenance are major obstacles. While Xpert MTB/RIF may be suitable for major reference hospitals, operational research is needed to evaluate the test and its additional yield above high-quality smear microscopy and clinical algorithms before it is used at the peripheral level.

In the meantime, The Union experts believe that direct microscopy should remain the initial diagnostic test for people suspected of having TB. In most LICs, the prevalence of RMP resistance among new TB patients is very low; an Xpert MTB/RIF result indicating RMP resistance will thus always need confirmation by another test.

In a population at high risk of RMP resistance (> 15%), however, the positive predictive value for RMP resistance by Xpert MTB/RIF is high, and identification of RMP resistance is an excellent proxy for multidrug-resistant TB (MDR-TB). The assay should be widely used for this purpose if, and only if, excellent MDR-TB management is available, both for ethical reasons and to reduce the risk of extensively drug-resistant TB.

This entire article is available at no charge:

Trébucq A, Enarson DA, Chiang CY, Van Deun A, Harries AD, Boillot F, Detjen A, Fujiwara PI, Graham SM, Monedero I, Rusen ID, Rieder HL. Xpert® MTB/RIF for national tuberculosis programmes in low-income countries: when, where and how? Int J Tuberc Lung Dis. 2011 Dec ; 15 (12): 1567–1572 .