[Use of the Xpert MTB/RIF test in routine screening of new cases of pulmonary tuberculosis in an endemic area].

Background: Developed initially for the diagnosis of multidrug-resistant tuberculosis, the Xpert MTB/RIF test has shown to be useful for the diagnosis of tuberculosis, especially among HIV-infected subjects. The objective of the study was to determine the contribution of the Xpert MTB/RIF test for routine pulmonary tuberculosis diagnosis in an endemic area.

Methodology: We undertook a prospective study among patients presenting with cough and sputum. The sputum was submitted to microscopic examination, to the Xpert MTB/RIF test and cultured by the Mycobacteria growth indicator tube (MGIT) technique. The study compared cases of pulmonary tuberculosis confirmed by a positive sputum culture and cases with cough but negative sputum culture.

Results: In multivariate analysis, the factors associated with positive cultures were the following: male gender, cough for more than 2 weeks, loss of weight and fever. The estimated clinical suspicion score consisted of 4 signs each having a coefficient of 1. The sensitivity of each clinical sign varied between 79 and 94%. In 348 cases of negative microscopic examination (composed of 295 cases with score<4 and 53 cases with score=4), the predictive positive value of the Xpert MTB/RIF was 80% for a score equal to 4 and 40.9% for a score<4. In cases of negative microscopic examination of the sputum, the Xpert MRT/RIF test should be undertaken if the score=4.

Conclusion: The diagnosis of tuberculosis in endemic zones could be improved by using the Xpert MTB/RIF.