Evaluation of Fluorescent Microscopy and GeneXpert MTB/RIF Assay for The Detection of Mycobacterium Tuberculosis Complex in Respiratory Specimen of Patients with ZN Smear Negative Pulmonary Tuberculosis

Objective: To evaluate the diagnostic validity of the GeneXpert for quick diagnosis of TB and recognition of Rifampin resistance in Ziehl–Neelsen smear-negative Broncho-alveolar lavage and sputum specimens obtained from suspected TB patients, keeping LJ culture as “Gold Standard”. Study Design: Cross sectional study. Place and Duration of Study: The study was conducted at Fatima Jinnah General and Chest Hospital (FJGCH), Quetta from January 2018 to December 2018. Materials and Methods: One hundred ZN-smear negative pulmonary specimens (63 BAL and 37 sputum) were collected from suspected TB patients (34% males and 66% females; mean age 52.8±18) visiting FJGCH, Quetta. The isolates were processed for fluorescent microscopy, LJ culture and GeneXpert according to standard protocol. Efficacy of these diagnostic tests for the detection of MTB was evaluated comparatively. Results: Out of 100 ZN smear-negative specimens; MTB was detected by FM in 18 (18%) samples while LJ culture detected MTB in 59 (59%) and GeneXpert in 55 (55%) samples. Conclusion: We concluded that GeneXpert is an innovative assay for prompt detection of MTB in smearnegative cases having higher sensitivity and specificity with additional advantage of drug resistance detection and turnaround time of two hours. The assay facilitates early diagnosis and appropriate management of TB to minimize morbidity and mortality.