Study of diagnostic role of GeneXpert test in patients with pulmonary tuberculosis at El-Mahalla Chest Hospital

Abstract

Background Tuberculosis (TB) is a serious health problem in middle-income and low-income countries and needs rapid diagnosis and treatment. Xpert MTB/RIF assay provides early results by simultaneous detection of Mycobacterium tuberculosis (MTB) and rifampicin (RIF) resistance. Aim To evaluate the performance of GeneXpert MTB/RIF technique in diagnosing patients with pulmonary TB at El-Mahalla Chest Hospital, Egypt. Patients and methods Data of pulmonary TB were retrospectively analyzed between February 2017 and February 2018 from patient files and included laboratory results regarding Ziehl–Neelsen (ZN) smear microscopy, GeneXpert assay, and culture. Patients were divided into group I, having confirmed TB, where MTB was detected, and group II, having unconfirmed and unlikely TB, where MTB was not detected. Results A total of 150 patients were recruited. Overall, 80% were males, and the median age was 45.2±15.1 years. Positivity of ZN smear for TB bacilli was 61.1%, positivity of GeneXpert MTB was 65.9%, and culture positivity was 67.3%. GeneXpert sensitivity and negative predictive value were 96 and 96%, respectively, and were found to be higher when compared with ZN smear with 89 and 90%, respectively. Specificity of both techniques was 100%. Previous history of TB was an independent predictor for GeneXpert positivity, whereas both previous history of TB and positive sputum smear were independent predictors of RIF resistance. Conclusion GeneXpert has a higher diagnostic value compared with ZN smear, providing a faster diagnosis for pulmonary TB than culture, and it can detect RIF resistance.