Valuing the use of GeneXpert test as an unconventional approach to diagnose pulmonary tuberculosis

Abstract

Background: A rapid, highly sensitive, and qualitative diagnostic test will significantly reduce the incidence of tuberculosis (TB). GeneXpert test is the test that is supposed to play this role with those specifications. Objective: Our goal was to assess the precision of the GeneXpert test in the diagnosis of pulmonary TB. Patients and methods: This cross-sectional analytic study was carried out at Assiut University Hospital in collaboration with Assiut Chest Hospital, Assiut, Egypt. A total of 67 patients of suspected pulmonary TB were included. For microbiological examination, two sputum samples were obtained from each patient within the same day. One sample was collected at Assiut University Hospital and subjected to smear microscopy by Ziehl—Neelsen staining and culture on Lowenstein—Jensen media. The other sample was taken at Assiut Chest Hospital to be processed for GeneXpert Mycobacterium tuberculosis/rifampicin assay. The culture was applied as a confirmatory test to evaluate the Xpert Mycobacterium tuberculosis/rifampicin assay test. Results: GeneXpert had 95.9% sensitivity and 94.4% specificity in diagnosing pulmonary TB with the area under the curve of 0.95 and overall diagnostic accuracy of 95.5%. Ziehl—Neelsen examination had 65.3% sensitivity and 100% specificity with the area under the curve of 0.83 and overall diagnostic accuracy of 74.6. For smear-negative, culture-positive cases, GeneXpert showed sensitivity of 94.1%. False-positive GeneXpert for TB was recorded in just one patient. Conclusion: The GeneXpert test is accurate in diagnosing pulmonary TB and its greatest benefit is clearly demonstrated in smear-negative TB cases. However, the test is not free from some fallacies, even if they are a few, which draws our attention to the importance of the conventional culture for TB and the clinical correlation.