Diagnostic performances of the Xpert MTB/RIF in Brazil.

BACKGROUND AND OBJECTIVES: As for all tests, the diagnostic performances of Xpert MTB/RIF might be different in settings with different tuberculosis prevalence. Aim of the study is to evaluate the performances of Xpert MTB/RIF to diagnose tuberculosis in Brazil, where 407 culture-confirmed tuberculosis patients were retrospectively enrolled in Rio Grande do Sul, between 2015 and 2016.

METHODS: Sensitivity, specificity, positive and negative predictive values of the test were calculated and a logistic regression analysis was performed to assess the role played by explanatory variables in the occurrence of true positive and negative diagnostic results.

RESULTS: Sensitivity of Xpert MTB/RIF was 100.0%, specificity 92.8%; positive and negative predictive values were 71.4% and 100.0%, respectively. In the HIV- infected sub-group specificity was 59.3%. In the multivariate logistic regression analysis, true positivity was associated with increasing age (1.0; p-value: 0.02) while true positivity and negativity were negatively associated with alcohol abuse.

CONCLUSIONS: Xpert is sensitive and specific in the Brasilian settings.