Comparative study between microscopic observation drug susceptibility and MTB/RIF Gene Xpert in the diagnosis of pulmonary tuberculosis in a specialized Egyptian hospital

Abstract

Background Diagnosis of pulmonary tuberculosis (PTB) is usually problematic regarding time and accuracy. Aim To compare between the microscopic observation drug susceptibility (MODS) and MTB/RIF Gene Xpert in sputum samples of PTB-suspect patients regarding sensitivity, specificity, timing to positivity, and drug susceptibility compared with the gold standard Löwenstein–Jensen (LJ) mycobacterial culture. Patients and methods This is a retrospective clinical study. Records of patients who were PTB suspect and who presented to El Maamoura Chest Hospital, Alexandria, Egypt, were reviewed between May 2016 and March 2018. Results MODS showed variable significance in prognostic performance compared with Gene Xpert regarding sensitivity (71.7 vs. 80.0%, respectively) and specificity (93.33 vs. 64.44%, respectively) compared with LJ culture. After exclusion of 29 patients who were at risk of having dead bacilli in their sputa, results showed near-similar prognostic performance between MODS and Gene Xpert regarding specificity (90.32% for both techniques) and sensitivity (72.88 vs. 79.66%, respectively). Gene Xpert showed overall superiority in time to positivity (within 3 h). MODS showed significant difference than LJ medium with timing to positivity from 7 to 22 days with mean±SD of 19.11±4.0 days. Conclusion For diagnosis of PTB, MODS was found to be more specific and relatively less sensitive compared with MTB/RIF Gene Xpert. With exclusion of sputum samples from patients who are at risk of having dead bacilli in their sputa, no significant difference was found between both techniques regarding sensitivity and specificity. MTB/RIF Gene Xpert has superiority in timing to positivity.