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.
Xpert MTB/RIF (Xpert), a new nucleic acid amplification test based on polymerase chain reaction (PCR), has been recently developed to detect Mycobacterium tuberculosis DNA and genetic sequences indicative of rifampicin resistance (i.e. mutations of rpoB). The entire PCR assay is performed automatically within a cartridge, where the sample and reagents are mixed. The test, which takes less than two hours, has 88% sensitivity for tuberculosis and 94% sensitivity for rifampicin resistance, as well as 98% specificity for both. In light of these advantages, the World Health Organization has recommended the use of Xpert for the diagnosis of tuberculosis in countries with high prevalences of human immunodeficiency virus (HIV) infection and multidrug-resistant tuberculosis (MDR-TB).
Brazil is considered a high-burden tuberculosis country (90 cases per 100 000 population). However, it is unusual among countries with a high tuberculosis burden in that primary MDR-TB is relatively uncommon (< 2%). Yet despite low rates of HIV co-infection (10%) and MDR-TB, the Brazilian National Tuberculosis Programme has recommended the incorporation of Xpert for the routine diagnosis of pulmonary tuberculosis in the public health system in an effort to increase the notification of cases with bacteriologically confirmed tuberculosis. To monitor the implementation of this new diagnostic test in the routine work of public health services, a roll-out pilot study was conducted. In this paper we report the lessons learnt during the introduction of Xpert in two cities. The results of the pilot study will be used to plan for the national scale-up of Xpert in Brazil and may be useful to other countries that are trying to incorporate this new technology.
