Operational lessons drawn from pilot implementation of Xpert MTB/Rif in Brazil

In health services in areas with a high burden of tuberculosis, diagnosis can be especially difficult because it takes several weeks or months to obtain the results of mycobacterial culture, which is the gold standard test for the diagnosis of tuberculosis. In such settings, diagnosis is usually based on microscopic examination of at least two sputum smears, but because sputum smear microscopy has low sensitivity, patients are often started on antituberculous therapy based on clinical evidence, without bacteriological confirmation. This leads to the underreporting of tuberculosis cases, unnecessary exposure to therapy with potential toxicity, and delay in the correct diagnosis and treatment of patients. In Brazil, around 26% of new tuberculosis cases are not confirmed with any bacteriological test and culture is not performed in 73% of re-treatment cases.