A Performance Assessment Study of Different Respiratory Samples for the Diagnosis of Pulmonary Tuberculosis (TB) using GeneXpert, Smear Staining, and TB Cultures

Abstract

Tuberculosis (TB) is one of the major re-emerging diseases. An increase in disease burden and subsequent misuse of anti-tuberculosis drugs has made the situation worse. Early diagnosis followed by antibiotic susceptibility testing can lower the increase in occurrence of multidrug-resistant (MDR). Conventional methods of diagnosing TB are laborious and time-consuming, so the present study was designed to evaluate the relative efficacy of conventional methods, including Ziehl-Neelsen (ZN) stain, fluorescent stain, BD Mycobacteria growth indicator tube (MGIT) liquid culture system, and molecular diagnosis via GeneXpert, using different respiratory samples. Results of the present study showed that A total of 642 samples were found positive via the BD MGIT Liquid cultures method, 483 using the ZN staining technique, 507 with the fluorescent staining technique, and 663 for GeneXpert, respectively. It was evident from the results that out of the samples tested, GeneXpert has a higher sensitivity than AFB smear microscopy and liquid culture methods in respiratory samples. GeneXpert can be a useful tool for early diagnosis of patients with high clinical suspicion of pulmonary TB. Positive GeneXpert, but culture-negative results should be read cautiously and well correlated with the clinical and treatment history of the patient. The other major advantage of GeneXpert is that it simultaneously detects Rifampicin (Rif) resistance and is especially beneficial in patients with MDR tuberculosis, and should be studied further. As False negative or false positive cases cause overuse of anti-TB drugs, leading to the emergence of MDR-TB. So, timely and accurate diagnosis is the key factor in the management of the disease, especially in countries like Pakistan with limited resources.